Scientific report [619678]

Scientific report
Regarding the enti re period of execution of the project

PN-II-RU-TE-2012 -3-0150: Investigation of the mesoscopic polar order and size effects in
driving polarization mechanisms of tunability in perovskites (IMPOTUN)

The objectives for the reporting period were:
O1. Modeling nonlinear dielectric properties of nanostructured ceramics with different grain sizes: 1.1. Potts
model implementation in order to describe the granulation growth in the nanostructured ceramics; 1.2.
Development of f inite element models for the calculation of local field in nanostructured ceramics; 1.3 Development
of a model for describing the nonlinear properties of relaxor nanostructured ceramics;
The purpose of this research is to investigate in terms of experiment al and theoretically the effects of nanoscale
grain size decrease on ferroelectric and nonlinear dielectric properties in ferroelectric ceramics. Study of di mensional
effects in fer roelectric ceramics are of major importance in two respects: (i) fundamenta l: finding the critical size
that sti ll allows for ferroelectricity at room temperature [1] and confirming the existence of the superparaelectric
state; (ii) miniaturization applicative in microelectronics for wireless devices.
For describing the role of g rain size on macroscopic dielectric properties from theoretical perspective we intend to
develop a model that takes into account the two essential characteristics of composites: microstructural
characteristics and local field inhomogeneity. For this two es tablished models in the literature, but never combined ,
were used: Potts model for accurate generat ion of polycrystalline structures and Finite Element Method (FEM) to
calculate the local electric fields that appear in material.
Potts Model
Potts model wa s recently proposed in the literature as a model that describes very accurate granular ceramic
growth s [2-5]. Potts model was initially proposed as a generalization of the Ising model to describe magnetic
materials with more than two possible states (Q) of spins . Potts ’s model Hamiltonian is:

ijSS
ijHδ
≠=−∑ , (1)
where {0,1, 2, , 1}iSQ∈− , 1
ijSSδ= if ijSS= or 0
ijSSδ= if ijSS≠ , and 1,iN= , where N represents the total
number of spins in the system. The evolution of such a system starts from a random ly initial configuration and is
allowed to evolve sequentially checking spin states by Metropolis procedure [6]. Monte Carlo Step (MCS) is the
elementary time in which N spins in t he system are verified.

Fig. 1 Time evolution of domains associated to a grain growth

Such a system development of 300×300 spins is represented in Fig.1 for different Monte Carlo steps. It is noted that
this domains development can be associated to a gra nular growth during which different grain sizes are obtained: 9 –
35 a.u. Thus the system is allowed to evolve until it reaches the desired average size.
Using this type of polycrystalline structure, can be developed a realistic model of ceramics where inter granular
boundaries are also added. (Fig. 2)

Fig. 2 Virtual ceramics with grains and grain boundaries subjected to boundary conditions of a plane- parallel
capacitor sides
This type of ceramics is used as "input" in FEM considering the boundary conditions of a plane-parallel side’s
capacitor. (Fig. 2)
Finite Element Method ( FEM )
The variation of electric potential inside a material without free charges is described by Laplace equation:
((, ) ) 0xy Vε∇⋅ ∇ = , (2)
where (, )xyε is loca l permittivity defined for nanostructured ceramics as it follows :
( ( , )) , inside grains(, ), on intergranular bound ariesnonlin local
linE xyxyεεε=
 , (3)
where 100lin granitaεε= = and (0) 1000nonlinε= .
The system of equations (2) and (3) is solved with the boundary conditions shown in Fig. 2 using FEM. Dur ing the
FEM procedure the system is divided into a number of elements and electric potential is calculated for nodes of elements using the Galerkin method [7 -9]. After this local electric field is calculated in each element.
FEM has been used in literature to describe the macroscopic electrical properties of the composite materials but has
never been applied to materials that contains one phase which presents a local permittivity dependent on local
electric field. In case of such a composite material (inclu ding nanostructured ferroelectric ceramics) equation (2)
becomes much more difficult to solve because the unknown equation, local electric potential, is introduced also in
local permittivity according to equation (3). FEM commercial software cannot describe this complex system of
equations and, therefore, it was necessary to develop a software that takes into account equation (3). Chosen
solution was to implement an iterative procedure based on FEM in which local permittivity and local fields are
calculated successively until the exact solution is reached ( novelty at international level ).

In Fig. 3 electric fields corresponding to ceramic with different granulations are represented. With grains size
decreasing it can be observed: increased inhomogeneity of t he electric field and local electric field decreasing on
ferroelectric core.

Fig. 3 Representation of local electric fields corresponding to ceramic with different granulations (GS = 30, 60, 90 and
single crystal). Electric field s intensity is represente d by the colors and the direction is perpendicular to the
equipotential black lines
After all the local electric fields have been calculated, effective permittivity of the material results from total energy of system formula calculated as the sum of local energy on elements:
2 2
1 22Ne
eff ii
ti
iE VAAdε ε
=∆⋅=∑ , (4)
where V∆ is the applied voltage, d – the distance between the electrodes , tA is the area of the 2D system , N e: the
total number of elements , iε: permit tivity, iE: local electric field,iA: area corresponding to the element .
In case of nonlinear composite s this permittivity is calculated for different applied fields and macroscopic
dependences of the effective permittivity and tunabilit y on the applied electric field are obtained (ratio between
zero field permittivity and permittivity for a given field). Such dependencies simulated for different grain sizes are
shown in Fig. 4.

0.0 0.5 1.0 1.5 2.0 2.5 3.0200300400500600700 GS = 90
GS = 60
GS = 30 Effective Permittivity
Applied electric field (a.u.)0.0 0.5 1.0 1.5 2.0 2.5 3.0200300400500600700 GS = 90
GS = 60
GS = 30 Effective Permittivity
Applied electric field (a.u.)0.0 0.5 1.0 1.5 2.0 2.5 3.01.01.52.02.53.03.5 GS = 90
GS = 60
GS = 30 Tunability
Applied electric field0.0 0.5 1.0 1.5 2.0 2.5 3.01.01.52.02.53.03.5 GS = 90
GS = 60
GS = 30 Tunability
Applied electric field
(a) (b)
Fig. 4 The role of grain size on permittivity dependencies (a) and tunabilit y (b) on the applied field
This combined model of Potts model and FEM managed to explain the changes induced by grain size decreasing on
the high field dielectric properties of relaxor and ferroelectric ceramics: decreasing of permittivity and tunability,
linearization of effective permittivity dependence on electr ic field and inflection point moving toward higher values
of applied electric field.
Some of these properties have already been observed experimentally, and others will be identified during the
project.

O2. Experimental study of grain size effect on dense nanocrystalline ceramics properties : 2.1 Synthesis and
micro/nanostructured characterization of perovskite nanopowders . Study of formation mechanisms ; 2.2
Micro/nanostructural and phase analysis; 2.3 Broadband low field dielectric characterization.
Achiev ing dense nanostructured ceramics with average particle sizes in the range of interest is necessary to study
from experimental point of view the ceramic grain size effects on nonlinear properties. Although in recent years the
study of dimensional effects h as attracted the researchers attention, very few publications have reported relevant
data for granulations under 400nm, this dimension being the technical limit for high density ceramics (> 95%) by
conventional sintering. Moreover, most publications report data for BaTiO 3 and less for other systems. In order to
obtain dense nanostructured ceramics, two conditions are required: (1) quality nanopowders obtaining, uncluttered,
with a narrow distribution by size; (2) a suitable densification technique which min imizes grain growth.
Nanopowders and nanostructured ceramics have been developed in collaboration with IENI- CNR & Univ. Genoa [10].
Ultrafine SrTiO 3 and doped SrTiO 3 nanopowders were prepared by direct precipitation (T<1000C; p=105Pa; pH ≈14 ),
according to reaction: SrCl 2+TiOCl 2+4NaOH→SrTiO 3+4NaCl+2H 2O. The final size of nanoparticles is determined by the
control of nuclei formation, crystallites growth and aggregation (by supersaturation, pH and temperature) [10]. SrTiO
3 and La -SrTiO 3 particles were obtained with sizes of approximately 15 nm which were used to produce dense
ceramics with dimensions smaller than 50nm by plasma sintering (Spark Plasma Sintering SPS [1]).
During the first part of experimental study following characterization were performed:
(a) Micro/nanostructur al and phase analysis that demonstrated purity phase and allowed the average grain size
determination.
(b) Broadband dielectric characterization at different temperatures, which highlighted the grain size effect on
the dielectric properties of nanostructured ceramics: permittivity decreasing and reduction of frequency
dispersive nature (Fig. 5). As it was expected, quatum-paraelectric character is maintained also for
nanostructured ceramics. Also, very low losses (tg δ< 0,7% at room temperature) throughout the whole
frequency range, makes these a good candidate material for the study of nonlinear phenomena. Preparation
and characterization of nanostructured ceramic such as pure phase SrTiO 3 and doped SrTiO 3 type wit h
nanometer gra nulation is inte rnationally novelty.

50 100 150 200 250 300100110120130140150
f= 1 kHz
f= 2 kHz
f= 10 kHz
f= 50 kHz
f= 105 kHz
f= 210 kHz
f= 500 kHz
f= 747 kHzReal part of permittivity
Temperature (K)La-STO
GS=40 nm
50 100 150 200 250 300180200220240260280300320
f= 1 kHz
f= 2 kHz
f= 10 kHz
f= 50 kHz
f= 105 kHz
f= 210 kHz
f= 500 kHz
f= 747 kHzReal part of permittivity
Temperature (K)La-STO
GS=50 nm

(a) (b)
50 100 150 200 250 3000.0020.0040.0060.008
f= 1 kHz
f= 2 kHz
f= 10 kHz
f= 50 kHz
f= 105 kHz
f= 210 kHz
f= 500 kHz
f= 747 kHzDielectric loss
Temperature (K)La-STO
GS=40 nm
50 100 150 200 250 3000.0000.0020.0040.0060.008GS=50 nm
f= 1 kHz
f= 2 kHz
f= 10 kHz
f= 50 kHz
f= 105 kHz
f= 210 kHz
f= 500 kHz
f= 747 kHzDielectric loss
Temperature (K)La-STO

(c) (d)
Fig. 5 Low field dielectric properties : (a,b) temperature dependence of the dielectric constant; (c,d) temperature
dependence of dielectric losses
Invest igation of high field properties of such nanostructured ceramics will be performed in the following steps, and
the obtained data will be published during the 2015 -2016 stages.
In the first stage were analyzed tunability properties of polymer -based nanocomp osite materials. Chitosan -gold type
nanocomposites were obtained by gold nanoparticles precipitation in the polymer and dielectric as well as tunability
properties were both analyzed from experimentally and theoretically point of view. The resul ts have bee n published
in ISI_1 paper, work which served as a model for other researchers in development of nanocomposite materials.
The chitosan -gold type nanocomposites were also investigated in terms of low field dielectric properties and
temperature dependence. T he results were correlated with morphology investigations and structural analysis which
confirmed the changes that were observed in both low field tunability properties. Such a composition –
microstructure -property correlation for polymer-based nanocomposite materials was performed for the first time at
international level and the results were published in the paper ISI_4.
Another polymer -based nanocomposite structure investigated was chitosan -BaTiO 3 in with the ferroelectric powder
has the size of hundreds n m and is responsible for modifying the dielectric properties and tunability of the polymer.
These materials have been the subject of papers published in this grant ISI_2.
O3. Investigation of BaM xTi1-xO3 type ceramics with ferroelectric -relaxor transition compositional induced: 1.1.
Preparation of BaTiO 3 type solid solutions by solid state reaction. 1.2 Micro/nanostructural and phase
characterization . 1.3 Study of the temperature dependence of dielectric properties using impedance spectroscopy.
1.4 Investigation via Raman spectroscopy and PFM -AFM nanoscale measurements of ferroelectric -relaxor transition
compositional induced .1.5 Study of the ferroelectric properties (P(E), sub-switching experiments ), and dc-tunability.
1.6 Using multiscale models for describing the polarization compositional induced in ferroelectric -relaxor systems.
To study the ferroelectric -relaxor transition from experimental point of view and its role on the nonlinear properties,

different BaM xTi1-xO3 type systems, where M=Zr, Sb, Sn we re investigated. BaZr xTi1-xO3 system received particular
attention, being one of the most studied systems in terms of transition to relax. One of the reasons that this system
is extensively studied is setting the limits between which the system behaves like a ferroelectric (x <0.15). like a
ferroelectric with diffuse phase transition (x <0.25) and like a relaxor (x> 0.30) [11]. These limits are very sensitive to
the preparation methods and microstructural features (density, grain size). On the other hand, th is system has
received special attention, in recent years, due to its tenability properties in paraelectric -relaxor phase. The origin of
the nonlinearity away from transition as well as the nonlinear behavior analysis of such a system in combination with
other linear dielectric materials is one of the most studied topics in recent years [11 -13].
Fine powders of BaZr xTi1-xO3 (BZT) with different concentrations of Zr (x=0.05, 0.10, 0.15, 0.20, 0.40) were obtained
by solid state reaction according to the reaction: () ↑+ →+−+− 2 3 1 2 2 3 )1( CO O TiZrBa xZrO TiOx BaCOx x (Fig.6a).
To avoid unnecessary crowding of powders the heat treatment of precursor powder mixtures was held at 9000C,
temperature sufficient to achieve complete reaction [14]. After calcination, the powders were milled and cold
isostatic pressed at a pressure of 1500 bar. The obtained samples were heat treated at 13000C and 15000C for 4
hours to obtain as good as possible densification. After sintering, the relative density of the ceramics was
determined by Archimedes method. For t he series sintered at 13000C were obtained densities between 90 -95%, and
for sintered series at high er temperature (15000C) were obtained densities around 95-98%. It has been observed
that with increasing of zirconium content a density decrease is achieve d in both series of ceramic s. Ceramics sintered
at 13000C were selected for further investigation because of lower grain sizes were obtained and the porosity is
acceptable for electrical measurements.
In first stage of the experimental study of BZT type cer amics following characterization were performed:
(a) Micro/nanostructural analysis has allowed average grain size determination for ceramics with low Zr
content (about 1 -1.5μm) and a decrease down to 0.5 μm for ceramics with high Zr content has been
observed. (Fig.6 b, x=0.40).
(b) Phase characterization, using x -ray diffraction has allowed the determination of perovskite pure phase
for all investigated ceramics, without appearance of other secondary phases within the limits of
detection of the diffractometer. (Fig. 6c)

Fig. 6 Flowchart for powders and ceramics and microstructural and phase characterization of BaZr xTi1-xO3-type
samples
In the second part of the experimental study on BZT type ceramics the tenability, electric and ferroelectric properties

were evalua ted.
The low field dielectric data showed the temperature change of ferro -para transition toward lower values with
increasing of Zr addition (Fig. 7a) and the trend toward relaxor character. It is noted that with increase of Zr content
the Curie temperatur e T C decreases from to 1100C (x=0.05) down to ~ -1100C (x=0.40). Dielectric losses are less than
6% in the whole frequency and temperatures range analyzed, which makes these ceramics proper candidate for tunable applications. To analyze the relaxor charact er of ceramics with high zirconium content the dielectric
properties were determined at several frequencies, and data were analyzed using the modified Curie -Weiss law (Fig.
7b). It can be seen that with increasing of zirconium content, the transition has a diffuse character and Maxwell –
Wagner type phenomena occurs at high temperatures. Also, the semi -empirical parameter η increases from 1.14 for
x=0.05 until 1.59 for x=0.40. This parameter has values close to 1 if the material is ferroelectric and close to 2 if
material is relaxor . In Table 1 all characteristics of the investigated ceramics are presented in detail . The obtained
results confirm s the transition to relaxor of the investigated system. This behavior was also confirmed by Raman
analysis carried ou t in collaboration with the University of Leoben, dr. Marco Deluca.

Fig.7 Low field dielectric properties : (a) temperature dependence of the permittivity, (b) Curie -Weiss low, (c,d)
temperature dependence of the permittivity for a few selected frequencie s
The next step was to determine the high field characteristics for these systems. Both switching properties (P (E)) and
field dependence of the dielectric constant were investigated. P(E) and minors a nalysis has highlighted the transition
to relaxor of the investigated system by reducing the hysteresis loop area and decrease the saturation and remnant
polarization with increasing zirconium content. As it can be seen in Figure 8 b,c, the hysteretic nature disappears at
room temperature and the ceramics have a linear nonhysteretic field decrease. Taking into account the low field
dielectric characteristics of these ceramics , can be concluded that BaM xTi1-xO3-type materials with a high M
concentration (in our case Zr) are excellent materials for nonlinearity applications by meeting the requirements of
nonhysteretic character , paraelectric phase at room temperature and low loss es. The only problem of these
materials is the high dielectric constant (for example, 3500 to x= 0.20) at room temperature. This problem c an be
solved by producing linear dielectric composite materials, as we show below .

Fig.8 P(E) loops and minors for BaZr xTi1-xO3 ceramics: (a) x=0.10; (b) x=0.20; (c) x=0.40
Nonlinearity characteristics of BaZr xTi1-xO3 type ceramics were taken at room te mperature and are presented in Fig.9.
As it can be observed, the hysteretic character disappears for x=0.20 and x=0.40 but still retains a strong permittivity
decrease with applied field. Moreover, the trend of saturation disappears, and in case of x=0.40 a nearly linear decrease of permittivity is obtained. As we have seen in previous studies [15,16] such behavior is obtained for
nanostructured materials and the appearance of such behavior to relax materials suggests that the field dependence
of permittivity cannot be explained using a paraelectric single phase model. For materials with low content of
zirconium have a hysteretic decrease of permittivity with a significant variation at low values of applied field.

Fig.9 Permittivity dependence on applied electric field for BaZr xTi1-xO3 ceramics: (a) x=0.10; (b) x=0.20; (c) x=0.40
To analyze the nonlinear behavior of BaZr xTi1-xO3 type ceramics multipolar model was used . This model applies to
solid solutions which have several contributions at nonlinearity mechanisms: a mechanism due to ferroelectric part
and a Langevin -type mechanism due to polarization clusters existent in solid solutions. Using this model allowed us
to determine the share of these two contributions, share which decreases from 21% for x=0.10 to 10% for x=0.20
(Fig.10) (international novelty ).

Fig.10 Theoretical fit of experimental data in the case of BaZr xTi1-xO3 ceramics : (a) x=0.10; (b) x=0.20.
The multipolar mechanism model cannot be used for x=0.40, its field dependence of permittivit y is only due to

extrinsically type of polarization because in this case are in relaxor state far away in paraelectric phase. Elucidating
the nature of nonlinear behavior of such materials is still being debated at international level, the behavior being
attributed to the nanoscale polarization clusters.
Also, multipolar mechanism model was used to analyze and interpret tunability properties of ferroelectric –
ferromagnetic composite materials such as Fe 2O3-BaTiO 3. These results represent novelty at internati onal level and
have been reported in a paper published in ISI journal (ISI_3), work that already has one citation.
Another solid solution studied in this project is Sb doped BaTiO 3. For ceramics produced in collaboration with
research group from University of Belgrade coordinated by prof. Bjliana Stojanovic , tunabilit y characteristics were
investigated, and experimental ly results were interpreted using Landau type models (Johnson approximation ). The
results are part of one ISI paper accepted for publication in ISI journal (ISI_6).
As was saying , the best materials for nonlinearity applications are compositions that are near ferroelectric –
paraelectric phase transition at room temperature with diffuse chara cter, such as ceramics with x= 0.20. The problem
with such material is the very high value of low field permittivity and the proposed solution is development of
composite materials with linear dielectric phase with low permittivity. Because so far there is no model to describe
tunability in composite materials with different inter -connectivities between component phases, we developed a 3D
model for tunability and permittivity description in linear ferroelectric/dielectric composites.
For the first time at international level a 3D FEM model that allows full inve stigation of the role of microstructure on
tunability properties in composite is developed. This model allowed generation of complex structures such as
random mixture of the two -phase composite with 0 -3 connectivity and 1 -3 connectivity with different anis otrop ies,
which is impossible to be achieved in 2D procedures.
In the case of the 3D model Laplace equation (2) and field dependence of permittivity (3) is solved by taking into
consideration the z component :
0)),,(( =∇ ⋅∇ Vzyxε
( ( , , )) , for tunable dielectric regio n(, ,) , for linear d ielectric phasenonlin local
linE xyzxyzεεε=

In MEF 3D, the system is divided into very small tetrahedral elements for which potential local electric fields are
calculated , ( gradV E−= ) and the effective permittivity is obtained from total energy and calculated as the sum of
local energie s on elements:
eNe
eee
teff E
dVωεωε∑
==

∆⋅
12 2
2 2
where V∆ is voltage applied to the virtual system , , d is the distance between electrodes , tω is the total volume of
the system, Ne is the number o f elements , and eε, eE respectively eτ are local permittivity, local electric field and
the volume element corresponding to e.

Using the 3D model have been created different types of connectivit ies (random mixture, 0 -3, 1-3), for the same
concentration of the two phases: 50% ferroelectric and 50% linear dielectric. For these particular microstructures were calculated the effective permittivity by using
10=linε for dielectric phase and ε=1000 for the ferroelectric one,
observing that the largest permittivity decrease is obtained when the ferroelectric phase is completely isolated in
the dielectric phase. The most inconvenient microstructure (highest permittivity) is obtained for colu mnar (1 -3) with
the dielectric phase in parallel with applied field. By c alculating tunability for these microstructures one observe that
a maximum of tunability is obtained for 1 -3 composite with the dielectric phase perpendicular on applied field ,
config uration which allows a reasonable decrease of weak field permittivity (Fig. 11b)
The simulations performed have shown that cannot get a control of tunability properties in absence of control of
microstructure and achievement of such composite materials leads to a tunability decrease together with reducing permittivity. Thus the achieved model proposes at international level for the first time a design of tunable
composite materials by controlling the microstructure and connectivity.

Fig.11 Effective pe rmittivity and tunability calculated for different configurations in linear ferroelectric/dielectric
composite
The results presented are subject of one ISI work under evaluation (ISI_7) and were an integral part of the doctoral
thesis sustained by one of t he project members (drd. Leontin Padurariu) in September. A significant part of the
doctoral thesis has presented numerical models for explaining the tunability properties of composite systems and
had explicitly reported the research project among funding sources .

O4. Ferroelectric -relaxor ceramics with different mixing degree: 1.1 Preparation of BaTiO 3 solid solution with
different mixing at mesoscale; 1.2 Study of low field dielectric properties by impedance spectroscopy method; 1.3
Study of broad band properties; 1.4 Raman spectroscopy investigation of ferroelectric -relaxor phase transition with
different degree mixing; 1.5 Using multiscale models for describing polarisation in ferroelectric -relaxor systems
For experimental study of infl uence of mixing degree on functional properties of ceramics with ferroelectric -relaxor
crossover 2 types of ceramics were investigated:
(i) BaZr xTi1-xO3 (BZT) solid solution with x=0.10, 0. 15 and 0.20, obtained by solid state reaction of oxide powders
BaCO 3, TiO 2 and ZrO2
(ii) BaZr xTi1-xO3 (BZT) solid so lution with same compositions ob tained by mixing perovskite powders previous
prepa red. We investigated:
• x=0.10 by mixing 0.5 BaZr 0.05Ti0.95O3 + 0.5 BaZr 0.15Ti0.85O3
• x=0.15 by mixing 0.5 BaZr 0.10Ti0.90O3 + 0.5 BaZr 0.20Ti0.80O3
• x=0.20 by mixing 0.2 BaZrO 3+0.8 BaTiO 3
This procedure was selected in order to obtain different mixing degree: for ceramics with 0.10 and 0.15 we were
expected to have more homogeneity than ceramics with x=0.20 .
All the powders were calcinated at 10000C/4h, after were grounded for de-agglomerated . After, the samples were
cold press at 1500 bar and thermal treatment at 15000C/4h in order to obtained dense ceramics. After sintering, the
relative density were determinate by Arhimedic method, and all th e samples have density of 95-98% .
Due to the fact that the microstructural and structural characteristics of x=0.10 and 0.15 are very similar , we will
present in the report only the data obtained for x=0.20. As it can be observed from XRD pattern (Fig.1 2) the peaks
for solid solution are sharp and well define, while the doublets at 45, 56, 65 and 75° 2θ from XRD for BZT obtained
by mixing perovskites are broad that indicate an overlapping of BZT with different compositions . Also, SEM images
for the two ceramics present major differences : if, the ceramics obtained from oxide reactive the microstructure is
compact, with only small intergranular pores, the ceramics obtained from perovskite mixing pr esent two distinct
regions one with large grains ~ 40 µ m that coexist with small grains ~ 1 µ m. This grain size difference is related to
inhomogeneity of Zr content: small grain correspond to BZT with large amount of Zr, while regions with large grains

correspond to BZT with small Zr content [14].

Fig.12 XRD pa ttern and SEM images for BaZr 0.20Ti0.80O3 ceramics
After microstructural characterisation the low field properties were investigated at different frequencies and
temperatures. In Fig. 13 are shown temperature dependence at f= 20 kHz, for all investigated samples. It can be observed that for ceramics with x=0.10 and 0.15 Curie temperature is the same (T
C=900C for x=0.10 and Tc=650C for
x=0.15) and only difference is a slight enlargement of phase transition for the ceramics obtained from perovskites. If
we used Curie-Weiss low for describing transition, we obtained an increase of η from 1.30 to 1.48 for x=0.10,
respectiv ely from 1.41 to 1.50 for x=0.15 and also for δ from 21 to 40 for x=0.10, respectiv ely from 26 to 48 for
x=0.15. These two semi-empiric parameters describe qualitatively the transition in ferroelectric -rela xor materials.
This enlargement is due to inhomogeneity of the ceramics obtained from perovskites mixing.
For composition x =0.20 the temperature dependence of properties changes dramatically: if the ceramics obtained
from oxides present a transition at Tc=500C, the samples from perovski tes show a very large transition with a small
modification of slop that correspond to two maximum: at 600C and 1100C. By comparing this data with that one
reported in literature these maximum will correspond to x=0.08 and x=0.18 Z r [14,17], that confirm the idea of a
mixing of BZT s with different compositions x=0.18 and x=0.08. This idea is confirmated also by data from XRD and
SEM.

20 40 60 80 100 120 140 16005000100001500020000250003000035000
oxide
perovskitesReal part of permittivity
Temperature (0C)x=0.10
20 40 60 80 100 120 140 1600500010000150002000025000300003500040000
oxides
perovskitesReal part of permittivity
Temperature (0C)x=0.15
20 40 60 80 100 120 140 160100020003000400050006000Real part of permittivity
Temperature (0C) oxides
perovskitesx=0.20

Fig.13 Temper ature dependence at f= 20kHz for BaZr xTi1-xO3 ceramics obtained with different mixing degree: (a)
x=0.10; (b) x=0.15 and (c) x=0.20

For a complete investigation of low field properties the frequency dependence in range 1 -106Hz was investigated for
tempera tures between 20 -1500C. As already shown in temperature dependence, ceramics with x=0.10 and 0.15
presented a similar behaviour so we decide to present here only the data for x=0.10. From Fig.14 (a) and (b) it can be

observed that real part of permittivity has no frequency dispersion even at low frequency (f=1 Hz), that confirm
electric homogeneity of the samples. Imaginary part of permittivity present a small Maxwell-Wagner phenomena
thermal activated, for frequency smaller than 100 Hz. This phenomena is i ndependent from process route, both
samples present this behaviour and it is most probably due to grain boundary, than compositional inhomogeneity.
100101102103104105106400080001200016000200002400028000Real part of permittivity
Frecquency (Hz)x=0.10
10010110210310410510605000100001500020000250003000035000Real part of permittivity
Frequency (Hz)x=0.10m

(a) (b)
100101102103104105106100101102103Imaginary part of permittivity
Frecquency (Hz)x=0.10
100101102103104105106100101102103104Imaginary part of permittivity
Frecquency (Hz)x=0.10m

(c) (d)
Fig.14 Frequency and temperature dependences of real and imaginary part of permittivity of BaZr 0.10Ti0.90O3 ceramics
obtained from: (a,c) oxides , (b,d) perovskites
An evident difference was obtained for ceramics with x=0.20. As it can be observed from Fig.15 frequency
dependence of imaginary part present a temperature dependent maximum for both ceramics. In case of BZT
obtained from perovskit es the imaginary part have two distinct components: (i) a dispersion at low frequency( below
100 Hz) that is more evident with increase temperatures maybe due to a spatial charge as M axwell- Wagner and (ii)
a maximum at medium frequency (~104-106 Hz) that decreases and shifts to higher frequency with increasing
temperature (Fig.15b).
1011021031041051060500010000150002000025000 Imaginary part of permittivity
Frequency (Hz)x=0.20
Increse temperature
10110210310410510604008001200160020002400
Increase temperatureImaginary part of permittivity
Frequency (Hz)x=0.20m

(a) (b)
Fig.15 Frequency dependence of imaginary part of permittivity for BaZr 0.20Ti0.80O3 ceramics obtained from : (a)
oxides, (b) perovskites

Both relaxation are thermal activated with different activation energy that can be calculate using Arrhenius 's low :
0
01exp2M
ME
f kTττπ= = , where 0τ is a pre-exponential factor . Using this low can be determine activated
energy for relaxation processes :
and
for ceramics obtained from oxides and
and
for ceramic with inhomogeneity . It can be observed that both ceramics
present two relaxation types : one at high temperature (i n paraelectric state ) with an energy of 0.5 eV that can be
correlated with conduction phenomena of grains and one at low temp eratures that is due to oxygen vacancies. The
smaller value for this energy in case of perovskite ceramics can be correlated with larger inhomogeneities in this
case.

Study of relaxation mechanisms in ferroelectric ceramics obtained from different sintering steps is a n ovelty at
international level and will be published in the next year. Before published this data was necessary to repeat the
experiments in different systems and to validate the results by multiple experiments.
For a complete understanding of the difference between samples we start to investigate the high field properties,
although this activity was first in the objectives for the next stage. As preliminary study we investigated the field dependent permittivity at room temperature and the results are shown in Fig. 16. As can be observed, for x=0.10
and x=0.15 it was obtained a changes of zero field permittivity and hysteretic behaviour for the samples prepared
from perovskites. At E=30kV/cm was obtained an increase of tunability from 2 to 2.5 for x=0.10, inhomogeneity
ceramics, while for x=0.15 a reduction from 3 to 2.5 was obtained . A first analysis cannot allow us to determine a
direct relation between ceramic inhomogeneity and tunability values, so for a better understanding temperature
dependence and different fitting models will be used for explain the mechanism that give the contributions.
For the sample with x=0.20 the changes in tunability behaviour are considerable. As first observation the sample
obtai n from perovskites has the zero field permittivity around 800, an excellent values for tunability applications.
Moreover, because this concentration is close to phase transition, a nonhisteretic behaviour was obtain for both
ceramics. Tunability value decr ease from 4 at E=25kV/cm in solid solution, to 1.8 in mixed ceramic. This behaviour is
related with mixed concentrations of BZTs in case of the last ceramic. The next investigation will allow us to
determine what mechanisms have the major contribution to n onlinear behaviour.

-40 -30 -20 -10 0 10 20 30 406008001000120014001600
oxides
perovskitesDielectric constant
E(kV/cm)x=0.10
-40 -30 -20 -10 0 10 20 30 4040080012001600200024002800Dielectric constant
E(kV/cm) oxides
perovskites x=0.15
-30 -20 -10 0 10 20 305001000150020002500300035004000Dielectric constant
E(kV/cm) oxides
perovskites x=0.20

(a) (b) (c)
Fig.16 Field dependenc e of dielectric constant for BaZr xTi1-xO3 ceramics with different mixing degree: (a) x=0.10; (b)
x=0.15; (c) x=0.20.
High field properties of ceramics with different mixing degree are novelty at international level and these results
are the subject of a ISI paper in preparation.

A very important part of the study of mechanisms that give contributions to nonlinear behaviour was investigation of
properties of Ba 1-xSrxTiO 3 ceramics with different porosity level. For explaining the role of microstructure to
nonlinear properties, the 3D model developed last year was used. It was calculate the permittivity values for
different microstructures : (i) columnar structures with cylindrical pores , (ii) 0 -3 with spherical pores perfect isolated
in ceramic matrix; (iii) layered structures . These microstructures were analysed as composite materials with 2
phases : ferroelectric matrix with permittivity 8000 and air inclusions with permittivity 1. For describe these complexe
structures it was necessary to generate virtual microstructure with elliptic pores. In contrast with other effective
field models, this approach can describe any microstructure by solving Laplace equation with Dirichlet and Neumann
boundary conditions . Using this method we calculated permittivity values for ceramics with different porosity level.
The simulation results allow to the authors to explain experimental data for the Ba1-xSrxTiO 3 ceramics with porosity
18% and 29%, that have a peculiar microstructure with perpendicular pores, similar with l ayered structures.

Fig.17 Effective permittivity vs. porosity calculate for different configurations: (a) columnar structures ; (b) close
spherical porosity (0 -3); (c) layered structures (2 -2) and (d) structures with layered porosity. In images dense r egions
are brown and pores are gray
The results were presented in paper ISI_7, paper reported to the present project . The modeling of low field dielectric
properties and nonlinear behaviour confirm the experimental data obtain for porous Ba1-xSrxTiO 3 cera mics. The
three members of the project (C. Ciomaga, L. Padurariu and L. Mitoșeriu) have a major contribution to realize and
completion o the paper, being the principal authors of the study.
A last investigation was Raman analysis of phase transition in ferroelectric -relaxor of BaZr xTi1-xO3. Raman
investigation is a nonele ctric method that confirm the transition to relaxor state by appearance of a new mode in
vibration spectrum. This maximum at 280 cm-1 appear for x =0.40 that is a relaxor at room temperature, while for
x=0.10 is not present. The Raman investigation was performed in collaboration with dr. Marco Deluca, from Leoben
University.

Fig. 18 Raman spectru for BaZr xTi1-xO3 ceramics at room temperature

Objectives for January – September 2016 : O5. Ceramics with ferroelectric -realaxor crossover and different mi xing
degree : 1.1 Study of ferroelectric properties (P(E), subswitching) and dc -tunability; 1.2 Multiscale modeling for
describing compositional induce polarisation in ferroelectric -relaxor systems .
In order to study from experimental and theoretic point of view polarisation mechanisms that gives contributions in
high field properties (P(E) and ε(E)) in ceramics with different mixing degree, BZT ceramics with x=0.10 and 0.15,
prepared in earlier stages and sintered at 15000C/4h. Field dependence of dielectric constant was investigated last
year and presented in Fig.16. In this stage we will pre sented the data analysing and models that explain the
experimental data. In Fig. 19 the field dependence of tunability ( n=ε(0)/ε(E)) was presented . As it can be observed,
the composition x=0.10, obtained by mixing perovskites present a strong nonlinearity , while in case x=0.15 the
nonlinearity is higher for the ceramics prepared by oxide mixing. This difference means different polarisation
mechanisms, that will be discuss using multipolar model.
0 5 10 15 20 25 30 35 401.01.52.02.53.0
oxide
perovskite mixingTunability, n
E(kV/cm)x=0.10
0 5 10 15 20 25 30 35 401.01.52.02.53.03.5
x=0.15
oxide
perovskite mixingTunability, n
E(kV/cm)
(a) (b)
Fig.19 Field dependence nonlinearity of BaZr xTi1-xO3 ceramics with different mixing degree : (a) x=0.10; (b) x=0.15
As mentioned above the multi polar model can separate between ferroelectric contribution (intrinsic contribution)
and extrinsic (Langevin type) due to nanopolar clusters. Because our ceramics have a strong inhomogeneity, we will
analysed both intrinsic an extrinsic contribution. For intrinsic contribution will use Johnson equation:
()()
()( )312 3 3
00 10
EE
βεεεε
+= , β – a parameter for nonlinearity
In this equation ()3 3
00εε=a and then logarithm. It becames :
()()()21log310 log log Ea E β ε ε +−=
We will represent () )) (log( log2E f E=ε . If the difference are only at extrinsic level the curves will be parallel ( β
parameter will be the same) , if the differences change the curves than also the intrinsic contribution is different. Fig.
20 present fits for 2 compositions .
0.5 1.0 1.5 2.0 2.5 3.0 3.52.752.802.852.902.953.003.053.10 x=0.10
oxide
perovskite mixinglog ε
log E2
0.5 1.0 1.5 2.0 2.5 3.0 3.52.72.82.93.03.13.23.33.4
oxide
perovskite mixingx=0.15log ε
log E2

(a) (b)
Fig. 20 The () )) (log( log2E f E=ε dependence for analysing the changes in intrinsic behaviour of nonlinear properties of
BaZr xTi1-xO3 ceramics with different mixing degree : (a) x=0.10; (b) x=0.15
It can be observed that, for ceramics with x=0.15 (Fig. 20 b), both curves are parallel, that means the same intrinsic
contribution. For composition x=0.10, the curves are different, means a change in β parameter , so a change of
intrinsic nonlinear character . Using this model, the changes in intrinsic contribution of nonlinear properties can be
determined. This model was proposed in literature as a possible method for analysed intrinsic contribution, but it is
for the first ti me when the model is used in case of two sets of ceramics with same composition and different
preparation route (novelty at international level ).
In order to understand the extrinsic contribution the multipolar model was applied. Using this model, the diff erent
contributions of nonferroelectric entities at nonlinearity can be determinated. By fitting experimental data it was
obtained in case of x=0.10 an increase of extrinsic contributions from 31% to 37% for the ceramics prepared by
perovskites mixing. This result is in agree with low field properties (Fig.13) where an increase of relaxor behaviour
was obtained in case of mixing perovskites ( nanopolar regions that depend after a Langevin low) .
0 5 10 15 20 25 306008001000120014001600Dielectric constant
E(kV/cm)x=0.10
Multipolar mechanism
Johnson eq.
0 5 10 15 20 25 30 35 404006008001000120014001600
Johnson eq.Multipolar mechanismDielectric constant
E(kV/cm)x=0.10m

(a) (b)
0 5 10 15 20 25 30 3550010001500200025003000
Johnson eq.Multipolar mechanismDielectric constant
E(kV/cm)x=0.15
0 5 10 15 20 25 30 354006008001000120014001600
Johnson eq.Multipolar modelDielectric constant
E(kV/cm)x=0.15 m

(c) (d)
Fig. 21 Ftting of experimental data with multipolar model for BaZr xTi1-xO3 ceramics: (a,b) x=0.10; (c,d) x=0.15.
The same increase of extrinsic contribution was observed for x=0.15 (from 31% to 34%). In conclusion, the ceramics
prepared from perovskites mixing have a large inhomogeneity at microscopic level, that gives an increase of polar
nanoregions, regions that have a Langevin type dependence. By combining, the results obtained from multipolar
model with Johnson fit, i t can be observed that in the case of composition x=0.10, the increase of nonlinearity is due
to changes in intrinsic contribution, while in case of x=0.15 only a small change in extrinsic contribution can be
observed. This type of analysis was for the fir st time performed during the present project . (novelty at international
level).
For a complete investigation of high field properties the P(E) loops were measured at room temperature for the
investigated ceramics. It can be observed that in case of x=0.1 0, P s and Ec are the same, and only a small difference
in Pr (that decreases for ceramic obtained from mixing perovskites) was obtained. In this case, a small increase of
hysteresis area (an increase of hysteretic losses) was obtained for mixing ceramics d ue to the higher

inhomogeneities. For composition x=0.15 the differences are: the ceramics obtained from mixing perovskites
increase the Ps from 1.31×10-7 C/mm2 to 1.58 x10-7 C/mm2, Pr from 2.93 x10-8 C/mm2 to 4.09 x10-8 C/mm2 and
coercitive field from 0 .10 kV/mm to 0.22 kV/mm.
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0-2.0×10-7-1.5×10-7-1.0×10-7-5.0×10-80.05.0×10-81.0×10-71.5×10-72.0×10-7B
E(kV/mm) oxide
perovskite mixingx=0.10Polarisation (C/mm2)
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0-2.0×10-7-1.5×10-7-1.0×10-7-5.0×10-80.05.0×10-81.0×10-71.5×10-72.0×10-7Polarisation (C/mm2)
E(kV/mm) oxide
perovskite mixingx=0.15

(a) (b)
Fig. 22 P(E) loops for BaZr xTi1-xO3 ceramics: (a) x=0.10; (b) x=0.15.

O6. Experimental study of size effect on nonlinear properties of dense nanocrystalline ceramics: 1.1 Study of
ferroelectric and nonlinear properties ; 1.2 Multiscale modelling ( Finite Element Method, Monte Carlo, Preisach).
Concerning nonlinear properties of nano crystalline ceramics, two type of systems were investigated: L a-SrTiO 3
ceramics investigated in first year of project and samples of (Ba,Sr)TiO 3 with core -shell structure and grain size
around few hundreds nm.
In case of La -SrTiO 3 ceramics it was observed a strong hysteretic behaviour of field dependence of dielectric contant,
and a strong nonlinearity at room temperature. Taking into account that SrTiO 3 is not tunable at room temperature
[18], and in case of nanocrystalline ceramics the nonlinearity was observed only for very high field 40 -80 kV/cm
[19,20], it can be concluded that La doping has improved nonlinear character of the system. Also, the dielectric
constant is very small, which would favor the use of this material in microelectronics application. The disadvantage is
the hysteretic behaviour and also a small reproductibility of the experimental data. Also, under electric field some
mechanisms of losses are activated and the total losses increase .
-30 -20 -10 0 10 20 308486889092949698100102104Dielectric constant
E(kV/cm)GS=40 nm
-30 -20 -10 0 10 20 301.001.051.101.151.20Tunability, n
E(kV/cm)GS=40 nm

(a) (b)
Fig. 23 Electric field dependence and tunability of La-SrTiO 3 ceramics with GS= 40 nm
Other investigated nanocrystalline system was ( Ba,Sr)TiO 3 ceramic with core -shell structure. In order to investiga te
the nonlinear behaviour in local graded structures, Ba0.50Sr0.50TiO 3 ceramics with core -shell structure were prepared
in collaboration with ICMATE -CNR, Genoa, coordinated by dr. Vincenzo Buscaglia. In thi s ceramic, the core is SrTiO 3
with 400 nm diameter and the shell – BaTiO 3. The obtained powder was densified using spark plasma sintering (SPS),
for avoid reactions at interfaces and grains growth. For comparison, one of the ceramic was resinterized at
13000C/48h, in order to obtain a homogeneous ceramic with grain size larger than 1 μm. The experimental results
for both cereamics are presented in Fig. 24 (a,b). It can be observed that homogeneous ceramic has a hysteretic

behavior in positive part of electr ic field and a nonlinearity of 1.8 at 40 kV/cm. Such hy steretic behaviour indicates
the present of ferroelectric regions even at room temperature , despute T C= -150C. The hysteretic behaviour nearly
disappears in the nanocomposite and the tunability, althou gh lower, still takes significant values, n = 1.22. It can be
noticed that the field dependence is linear, unlike in case of nanocrystalline La-SrTiO 3. In our previous papers, in
nanocrystalline BaTiO 3 ceramics, the linearisation was observed for very high fields (80-100 kV/cm). Also, in this case
the tunability is high for a nanoceramic material.
-40 -20 0 20 4060080010001200140016001800Dielectric constant
E(kV/cm)NanocompositeHomogeneous ceramic
-40 -20 0 20 401.01.11.21.31.41.51.61.71.8Tunability, n
E(kV/cm)Homogeneous ceramic
Nanocomposite

(a) (b)
Fig. 24 (a) Field dependemce perm ittivity for both types of (Ba,Sr)TiO 3 ceramics; (b) Field dependence tunability
The experimental results presented in this section are novelty at international level, and are included in a ISI paper
(ISI_9 – under review ).
An important part of the present project was development of 3D FEM models to design composite materials with
tunable properties. In last years, the developed models explained the role of interconnectivity on the nonlinear
properties. In this year, the models explain the role of permitt ivity values of linear dielectric on the tunability
properties and the role of composition. It was for the fi rst time at international level, when a such model was
development and the results were published in the paper ISI_8. This paper was entirely perfo rmed by project team.
The paper was published in Acta Materialia , journal placed in Top 1 in l UEFISCDI range, domain Metallurgy &
Metallurgical Engineering .
The main results were: for random microstructures with diffferent concentration of linear dielect ric inclusion, by
increasing concentration of linear phase a decrease of permittivity was observed, while the tunability is almost
constant up to 40% of linear dielectric, and after a strong decrease appears. The results were obtained by
considering the permittivity of paraelectric matrix of 1000 and permittivity of linear dielectric 10. These types of
materials can be used for explain nonlinear properties in solid solution with high inhomogeneity.

Fig. 25 (a) Field dependence effective permittivity of a composite materials linear dielectric – paraelectric with random
microstructure ; (b) Field dependence of tunbality with linear dielectric addition at E=30kV/cm.
Other important result was theoretical investigation of role of permittivity values on the tunability properties. In this case the connectivity was random and the concentration of the linear dielectric phase was 50%. The results show
that by decreasing the permittivity value of dielectric phase, a reduction of effective permittivity was obtained.

Taking i nto account the present results, the porous materials seems to be an optimum in tunability applications.
Also, for the nanostructured materials the control of grain boundary significand modified the properties
(concentration of boundary and composi tion) .

Fig. 26 (a) Effective permittivity, (b) tunability vs. applied electric field for a random structure with 50%- 50% composition, and
for the permittivity of dielectric phase between 1 and 200
The present project gives important contributions a t international level concerning design and preparation of
tunable materials with controlled properties. Also, important contributions to understand polarisation
mechanisms and development of models to explain high field properties.

ISI papers published in grant topics (acknowledgements PN -II-RU -TE-3-2012-0150)
ISI_1. Ana Cazacu, Lavinia Curecheriu , Alexandra Neagu , Leontin Padurariu , Adrian Cernescu, Isabelle Lisiecki, Liliana
Mitoseriu , Tunable gold -chitosan, nanocomposites by local field engineering, Applied Physics Letters, 102, 222903
(2013) (50% cu PN -II-ID-PCE -2011-3 -0745) IF=1,757
Cited by : 1
1. Sa, Tongliang; Cao, Ziping; Wang, Yongjin; et al., Enhancement of charge and energy storage in PbZrO3
thin films by local field engineering, Applied Physics Letters, 105, 043902, 2014

ISI_2. Alexandra Maria Neagu , Lavinia Petronela Curecheriu , Ana Cazacu, Liliana Mitoseriu , Impedance analysis and
tunability of BaTiO3 -chitosan composites: towards active dielectrics for flexible electronics , Composite Part B:
Engineering, 66, 109-116, (2014) (50% cu PN -II-ID-PCE -2011-3 -0745) IF=1,301
ISI_3. Lavinia Curecheriu , Petronel Postolache, Maria Teresa Buscaglia, Vincenzo Buscaglia, Adelina Ianculescu,
Liliana Mitoseriu , Novel magnetoelectric ceramic composites by c ontrol of the interface reactions in Fe 2O3@BaTiO 3
core -shell structures, Journal of Applied Physics, 116, 084102 (2014), IF=2,185
Cited by : 3
1. Li, X.; Guo, F.; Wang, S. Y.; et al. Template-free synthesis of Nd0.1Bi0.9FeO3 nanotubes with large inner
diameter and wasp -waisted hysteresis loop, Applied Physics Letters, 107. 062903 (2015)
2. Lopez -Ortega, Alberto; Estrader, Marta; Salazar -Alvarez, German; et al. Applications of exchange
coupled bi -magnetic hard/soft and soft/hard magnetic core/shell nanoparti cles, Physics Reports-Review
section of Physics Letters, 553, 1 -32 (2015)
3. Wang, J.; Rong, G. J.; Liu, L.; et al. Dielectric properties of Mn-doped BaTiO3 -based ceramics synthesized
by wet chemical method, PROCEEDINGS OF THE 5TH INTERNATIONAL CONFERENCE ON ADVANCED
DESIGN AND MANUFACTURING ENGINEERING Book Series: AER -Advances in Engineering Research, 39,
716-719 (2015)

ISI_4. Alexandra Maria Neagu , Lavinia Petronela Curecheriu , Mirela Airimioaei, Ana Cazacu, Adrian Cernescu, Liliana
Mitoseriu , Impedan ce spectroscopy characterization of relaxation mechanisms in gold -chitosan nanocomposites ,
Composite Part B: Engineering 71, 210 -217 (2015) (50% cu PN -II-ID-PCE -2011-3 -0745) IF=1,301
Cited by : 3
1. Saravanan, Annamalai; Ramasamy, Radha Perumal Investigatio n of polymer dynamics in chitosan –
maghemite nanocomposites: a potential green superparamagnetic material, Journal of Polymer Research,
23, 5, 104, 2016
2. Safari, Salman; van de Ven, Theo G. M. Effect of Water Vapor Adsorption on Electrical Properties of
Carbon Nanotube/Nanocrystalline Cellulose Composites, ACS Applied Materials&Interfaces, 8, 9483 -9489
(2016)
3. Begum, S. N. Suraiya; Aswal, Vinod K.; Ramasamy, Radha Perumal , Small-Angle Neutron Scattering and
Spectroscopic Investigations of Ag Fractal For mation in Chitosan -Ag Nanocomposite Facilitated by
Hydrazine Hydrate, Journal of Physical Chemistry C, 120, 4, 2400-2410 (2016)

ISI_5. Lavinia Petronela Curecheriu , Maria Teresa Buscaglia, Filippo Maglia, Umberto Anselmi-Tamburini, Vincenzo
Buscaglia, Liliana Mitoseriu , Design tunable materials: ferroelectric -antiferroelectric composite with core -shell
structure , Applied Physics Letters, 105, 252901 (2014) (50% cu PN -II-ID -PCE -2011-3 -0745) IF=1.650
ISI_6 . Lavinia Petronela Curecheriu, Vijatović Petrović M .M, Bobic J.D, Stojanović B., Nonlinear properties of
antimony doped BaTiO 3 ceramics, Applied Physics A, 119, 681-686 (2015) IF= 1,444
ISI_7. Roxana Stanculescu, Cristina E. Ciomaga , Leontin Padurariu ,Pietro Galizia, Nadejda Horchidan, Claudio Capian i,
Carmen Galassi, Liliana Mitoseriu , Study of the role of porosity on the functional properties of (Ba,Sr)TiO 3 ceramics,
Journal of Alloys and Compounds, 643, 79 -87 (2015) IF= 3,014
Cited by : 2
1. Cao, Yunpeng; Li, Shuying; Li, Fei, Effect of the sinteri ng temperature on the phase transition behavior
and electrical properties of (Ba0.8Sr0.2)TiO3 ceramics, Journal of Materials Science – Materials in
Electronics, 27, 8, 8710-8716 (2016)
2. Ianculescu, A.; Pintilie, I.; Vasilescu, C. A.; et al. Intrinsic pyro electric properties of thick, coarse grained
Ba1-xSrxTiO3 ceramics, Ceramics International, 42, 8, 10338-10348 (2016)

ISI_8. Leontin Padurariu, Lavinia Curecheriu, Liliana Mitoseriu , Nonlinear dielectric properties of paraelectric –
dielectric composites de scribed by a 3D Finite Element Method based on Landau-Devonshire theory, Acta Materialia
103, 724-734 (50% cu PN -II-ID-PCCA -2013-4 -1119) IF=2,529

ISI papers send in project field (acknowledgements PN -II-RU -TE-3-2012-0150)
ISI_9 . Mirela Airimioaei,Maria T eresa Buscaglia, Ilenia Tredici, Umberto Anselmi-Tamburini, Cristina Ciomaga,
Lavinia -Petronela Curecheriu, Andreja Benčan, Vincenzo Buscaglia, Liliana Mitoseriu, BaTiO 3-SrTiO 3 nanocomposites
with temperature independent permittivity and linear tunability , ACS Applied Materials & Interfaces
Book Chaper
Leontin Padurariu, Liliana Mitoseriu, ”Local field engineering approach for tuning dielectric and ferroelectric
properties in nanostructured ferroelectrics and composites ”, in Nanoscale ferroelectrics and multiferroics: Key
processes and characterization issues, and nanoscale effects, Wiley and Sons ISBN: 978 -1-118-93575-0, p. 588-611
(2016) (50% with PN-II-ID-PCCE -2011-2 -0006)

Presentations at international conferences: 1 Invited, 14 orals , 16 poster s
1. L.P. Curecheriu , A. Cazacu, Al. Neagu , L. Padurariu and L. Mitoseriu , Tunable chitosan -based nanocomposite by
local field engineering, COST SIMUFER Action MPO904 Workshop Advances in Ferrolectrics and Multiferroics,
Prague, Czech Republic, Institute of Phy sics AS CR, 21 July 2013 (oral presentation)
2. A. M. Neagu , C. Padurariu, L. P. Curecheriu , L. Mitoseriu , Impedance analysis and tunability of BaTiO3 -chitosan
composites: towards active dielectrics for flexible electronics, IEEE – ROMSC Conference – 10th E dition 2 -3 September
2013 (poster presentation) (partial with PN-II-ID -PCE -2011-3 -0745)
3. C. E. Ciomaga and L. Mitoseriu , Synthesis and functional properties of ceramic composites: Experiment and
modeling, IEEE- ROMSC Conference – 10th Edition 2 -3 September 2013 (invited presentation) (partial with PN II-ID –
2011-3 -0745, PNII -ID-PCCE -2011-2 -0006)
4. Z.V. Mocanu, L. P. Curecheriu , C. E. Ciomaga and L. Mitoseriu , Comparative study of the influence of sintering
temperature on the functional properties of BaCexTi1 -xO3 ceramics, IEEE- ROMSC Conference – 10th Edition 2 -3
September 2013 (poster presentation) – PN-II-ID -PCE -2011-3 -0745
5. L.P. Curecheriu, L. Mitoseriu , Dc-electric -field dependence of dielectric constant in relaxor ferroelectric systems,
COST SIMUFE R Action MPO904 Workshop, Kraków, Poland, 2 -3 september 2013 (poster)
6. L. Padurariu, L. Mitoseriu , Electrical properties of ferroelectric composites in terms of local field imhomogeneity,
COST SIMUFER Action MPO904 Workshop, Kraków, Poland, 2 -3 september 2013 (poster)
7. L. Padurariu, L. Curecheriu , V. Buscaglia, L. Mitoseriu , Grain size effect on nonlinear properties in nanostructured
ferroelectric ceramics: modelling and experimental validation, 13th International Meeting on Ferroelectricity,
Kraków, Po land, 2 -6 september 2013 (oral presentation)
8. L.P. Curecheriu , V. Musteata, M.T. Buscaglia, V. Buscaglia, L. Mitoseriu, Influence of the lengthscale cation mixing
degree on the nonlinear dielectric properties of BaZr xTi1-xO3 ceramics, 13th International Meeting on Ferroelectricity,
Kraków, Poland, 2 -6 september 2013 (oral presentation)
9. L.Padurariu , C. Galassi, L. Mitoseriu , Investigation of the role of porosity on the switching properties of Nb -PZT
ceramics: experiment and modeling, 10th Student Meeti ng, Novi Sad, Serbia, 6 -9 November 2013 (oral presentation)
(partial with PN-II-ID -PCE -2011-3 -0745)
10. A. Neagu , L. Padurariu , L. Curecheriu , L. Mitoseriu , Dielectric properties of polymer matrix nanocomposites, The
Third Early Stage Researchers Workshop” COST MP0904 – SIMUFER Novi Sad, Serbia, 6 -9 November 2013 (oral
presentation)
11. L.Padurariu , C.Galassi, L.Mitoseriu , Modeling of the Dielectric Properties of Porous Ferroelectric Structures,
Closing Conference COST MP0904 – SIMUFER, CNR -IENI, 30th Janua ry-1st Feburary 2014, Genoa, Italy (oral)
12. L. Curecheriu , M.V. Pop, M.T. Buscaglia, V. Buscaglia , L. Mitoseriu , Ferroelectric -relaxor crossover effects on the
nonlinear dielectric properties and switching character in BaZr xTi1-xO3 ceramics, Closing Conf erence COST MP0904 –
SIMUFER, CNR-IENI, 30th January -1st Feburary 2014, Genoa, Italy (poster) (partial cu bilateral Romania -Italia
643/1.01.2013)
13. M.T. Buscaglia, V. Buscaglia, L. Curecheriu , C. Padurariu, M.V. Pop, L. Mitoseriu , Antiferroelectric -ferro electric
composite ceramics with novel functional properties, Closing Conference COST MP0904 – SIMUFER, CNR -IENI, 30th
January -1st Feburary 2014, Genoa, Italy (poster) (partial cu bilateral Romania -Italia 643/1.01.2013)
14. L.Padurariu , L.Mitoseriu , Using Finite Element Method for Material Design: Tailoring Permittivity and Tunability
of Ferroelectric Based Composites, COST IC1208 Workshop, 20th -21th March 2014, Santarem, Protugal (oral)
15. L. Padurariu, L. Mitoseriu , Tunable composites materials designed by local field engineering, Electroceramics XIV,
16-20 June 2014, Bucharest, Romania (oral)

16. F. Gheorghiu, C.E. Ciomaga, L. Curecheriu , S. Feraru, M. N. Palamaru, V. Musteata, N. Lupu and L. Mitoseriu ,
Study of structural and electrical properties of do uble perovskite Sm 2NiMnO 6 multiferroic ceramics, Electroceramics
XIV, 16-20 June 2014, Bucharest, Romania ( poster ) (partial with PN -II-ID -PCE -2011-3 -0745)
17. C. E. Ciomaga , M. Airim ioaei, R. Tanasa, C. Galassi, L. Mitoseriu , Study of magnetic and dielectr ic properties of
MnFe 2O4- ferroelectric ceramic composites, Electroceramics XIV, 16 -20 June 2014, Bucharest, Romania ( poster )

18. L. Curecheriu , M.V. Pop, M.T. Buscaglia, V. Buscaglia , L. Mitoseriu , Ferroelectric -relaxor crossover effects on the
nonlinear dielectric properties and switching character in BaZr xTi1-xO3 ceramics, Electroceramics XIV, 16 -20 June
2014, Bucharest, Romania (oral) (partial cu bilateral Romania -Italia 643/1.01.2013)
19. M.T. Buscaglia, V. Buscaglia, L. Curecheriu , C. Padurariu, M.V. Pop, L. Mitoseriu , Antiferroelectric -ferroelectric
composite ceramics with novel functional properties, Electroceramics XIV, 16 -20 June 2014, Bucharest, Romania
(poster) (partial cu bilateral Romania -Italia 643/1.01.2013)
20. R. Stanculescu, C. E. Ciomaga , C. Galassi, L. Mitoseriu, Functional properties of graphite -derived porous BaSrTiO 3
ceramics, 14th International Balkan workshop on applied physics, Constanta, 2 -4 july 2014 (poster )

21. L.P. Curecheriu, L. Padurariu, L. Mitoseriu , Nonlinear dependence of dielectric constant in polymerbased
composite, European Conference on Application of Polar Dielectrics 7 -11 July 2014 – Vilnius, Lithuania (oral)
22. C. E. Ciomaga , M. Airimioaei, L. P. Curecheriu , M. T. Buscaglia, V. Buscaglia, L. Mitoseriu , Dielectric and non -linear
properties of SrTiO 3@BaTiO 3 core -shell ceramic, European Conference on Application of Polar Dielectrics 7 -11 July
2014 – Vilnius, Lithuania (oral)
23. L.P. Curecheriu , M.T. Buscaglia, V. Buscaglia, C. Padurariu, L. Mitoseriu , Combining ant iferroelectric -ferroelectric
in composite in searching new functional properties, European Conference on Application of Polar Dielectrics 7 -11
July 2014 – Vilnius, Lithuania (poster)
24. R. Stanculescu, C. E. Ciomaga , C. Galassi, L. Mitoseriu , The role of porosity on the functional properties of
BaSrTiO 3 ceramics, Autumn School on Physics of Advanced Materials (PAMS1), Iasi 2014, (poster)
25. L.P. Curecheriu , L. Padurariu , M. T. Buscaglia, V. Buscaglia, L. Mitoseriu , Non -linear dielectric properties in
ferroelectric -based ceramics: material design, experiment and modelling, TO-BE Spring Meeting 2015, MP1308 COST
Action TO -BE, Aveiro, Portugalia, 30 March -2 April 2015 (poster)
26. R. Stanculescu, C. E. Ciomaga , N. Horchidan, C. Capiani, C. Galassi, L. Mitoseriu , Oxygen vacancies -related
dielectric response of Ba 0.70Sr0.30TiO 3 ceramics, 14th I nternational Conference European Ceramic Society, 21 -25 June ,
2015, Toledo, Spain (poster)
27. C. E. Ciomaga, L. Padurariu, L. P. Curecheriu , I. Lisiecki, M. Deluca, C. Galassi , L. Mitoseriu , Using multi -walled
carbon nanotubes in spark plasma sintered ferroelectric ceramics for tailoring dielectric and tunability properties,
The 8th I nternational Conference on Advanced Materials : ROCAM 2015 7-10 July 2015, B ucuresti , Romania (oral).

28. L. Padurariu, L. Curecheriu, V. Buscaglia, L. Mitoseriu , Modeling the size effects on the nonlinear dielectric
properties in nanostructures ferroelectric, ceramics, The 8th International Conference on Advanced Materials:
ROCA M 2015 7-10 July 2015, Bucuresti, Romania (oral).

29. L. Padurariu, L. Curecheriu, L. Mitoseriu, Nonlinear dielectric properties of ferroelectric -dielectric composites
described by a 3D Finite Element Method based on Landau -Devonshire theory, 3rd Internat ional School of Oxide
Electronucs, Cargese, Franta, 12 -24 October (2015) (poster)
30. L.P. Curecheriu , M.T. Buscaglia, V. Buscaglia, G. Canu, L. Mitoseriu , Preparation and functional properties of
Ba0.85Ca0.15Zr0.10Ti0.90O3 ceramics with different grain si ze, Electroceramics XV, 27 -29 June 2016, Limoges, France (oral)
31. L.P. Curecheriu, C.E. Ciomaga , N, Horchidan, M. Simenas, L. Mitoseriu , Effect of Fe doping on the ferroelectric –
relaxor crossover in BaZr xTi1-xO3 ceramics, European Conference on Applicati on of Polar Dielectrics , 21-25 August
2016, Darmstad, Germania (poster)
Doctoral thesis finalized:

Leontin Padurariu , Numerical models to describe the ferroelectric and dielectric properties of composite systems ,
Sept. 2014, Universit y „Alexandru Ioan Cuza” of Iasi, coord inator: prof. dr. Liliana Mitoseriu ( acknowledgements at
CNCS -UEFISCDI PN-II-RU -TE-2010-187, CNCS -UEFISCDI PN-II-ID -PCE -2011-3 -0745, CNCS -UEFISCDI PN -II-RU -TE-2012-
3-0150, CNCS -UEFISCDI PN-II-ID -PCCE -2011-2 -0006). Thesis was awarded by „Alexandru Ioan Cuza” University with
the diploma of excellence.

Original results obtained during the project were:
• publication of 8 papers in journals with impact factor (ISI WoS), with a total factor IF total= 15.181 ( score
calculated on the number of r esearch grants that have contributed to the works ). The papers have 9
citation in ISI WoS journals.
• participation with 31 papers at international conference: 1 invited, 14 orals and 16 posters. One of the
poster was awarded by the Romanian Society of Physi cs (SRF)
• publication of a book chapter in ISI publisher
• one PhD thesis in project field .

References
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Appl. Phys. Lett. 88, 252905 ( 2006); X.H. Wang et al., J. Am. Ceram. Soc., 89 [2] 438– 443 (2006)
[2] R.B. Potts, Proc. Camb. Phil. Soc. 48 106,(1952).
[3] M.P. Anderson, D.J. Srolvitz, G.S. Grest, P.S. Sahni, Acta Metall. 32 783(1984). [4]Q. Yu, S.K. Esche, Comput. Mater. Sci. 27 259(2 003).
[5]C. Ming Huang, C.L. Joanne, B.S.V. Patnaik, R. Jayaganthan, Applied Surface Science 252 3997 –4002 (2006).
[6]N. Metropolis, A. W. Rosenbluth, M. N. Rosenbluth, A. H. Teller, and E. Teller, J. Chem. Phys. 21, 1087 (1953)
[7] M. S. Gockenback Society for Industrial and Applied Mathematics "Understanding and Implementing the Finite
Element Method"(2006)
[8] A. C. Polycarpou "Introduction to the Finite Element Method in Electromagnetics" Morgan & Claypool (2006)
[9] E. Becker et al. "Finite Elements A n introduction" ( Prentice -Hall) (1981)
[10] V.R. Calderone et al. Chem.Mater. 18, 1627 -1633 (2006)
[11] Q.Xu, et al. Acta Mater. 61 4481-4489(2013)
[12] X.J. Chou et al. , Ceram. Int. 34 911 (2008)
[13] P.R. Ren, et al. Mater. Res. Bull. 46 2308, (2011)
[14] C.E. Ciomaga, J.Eur.Ceram.Soc. 27, 13 -15, 4061-4064 (2007)
[15] L.P. Curecheriu, et al. Appl.Phys.Lett. 97, 242909 (2010)
[16] L. Padurariu, et al. Phys. Rev. B 85, 224111 (2012)
[17] J. Ravez, C. Broustera, A. Simon, Lead -free ferroelectric relaxor cer amics in the BaTiO
3-BaZrO 3-CaTiO 3 system, J.
Mater. Chem. 9, 1609 (1999)

Project manager,
Asist.dr. Lavinia Petronela Curecheriu
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