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The effect of grain size was not fully explored in composites containing ferroelectric and magnetic phases including the independent properties of each phase. Aiming to study the dependence of ferroic and multiferroic properties with average grain size in composites this work reports preparation method and electric, magnetic and magnetoelectric properties of particulate composites with distinct combination of grain size of each phase. A new sintering method was applied to prepare a group of samples with distinct configuration of grain size distribution. With this method it was possible to densify ceramics avoiding grain growth using spark plasma sintering. It was observed that the all ferroic and multiferroic properties were correlated with the setup of grain size of each phase in the composite, by example the dependence of magnetic properties with the electric phase grain size. Besides it was noticed that is possible to improve magnetoelectric coefficient by changing grain size of both phase, even inducing the self-biased effect by decreasing the grain size of the ferroelectric phase.

Doped and un-doped 0.5% Er3+ ferroelectric ceramics (1-x)[Pb(1-y)Lay(Mg1/3Nb2/3)O3]-xPbTiO3 (PLMN-PT) were prepared via solid-state reaction using the columbite method and densified by means of conventional sintering (CS), uniaxial hot pressing (HP), and spark plasma sintering (SPS). We review and discuss the influences of the densification process on the microstructural, structural, and dielectric properties of the ceramics. Samples with no porosity or grain size changes caused by the densification process were observed. A density of the ceramics close to the theoretical value (more than 99%) was reached with HP. The heat treatment process in ceramics through SPS eliminates the dark color and improves transparency. Furthermore, the influence of the densification process on the microstructural and structural properties of the ceramics was reviewed and discussed, finding that the electrical properties are favored by HP.

The relation between the nonlinear dielectric permittivity $$\varepsilon '(E)$$ and the macroscopic polarization P(E) is obtained for ferroelectrics considering a weak alternating electric field $$E_1\cos (\omega t)$$ superimposed to a dc bias field $$E_0$$ . Two different empirical models are reviewed. The first model uses the hyperbolic tangent function to represent the hysteretic behavior of the macroscopic polarization. In the second model is assumed that the dielectric permittivity is proportional to the reciprocal of a quadratic function of the local field, i.e., $$\varepsilon ' \propto {\{\alpha +\beta {\left[ E+\kappa P(E)\right] }^2 \}}^{-1}$$ . A combination of both models is used to fit the experimental curve $$\varepsilon '(E)$$ and to reproduce P(E). The parameters obtained from the fitting with this model can be used to get a better understanding of the correlation between the macroscopic response and the domain structure.

Multiferroic Bi0.85La0.15FeO3 powders and ceramics were synthesized under extreme conditions by a combination of high-energy ball cryomilling, fast firing and spark plasma sintering procedures. Single-phased and perovskite structured samples, where both rhombohedral (R3c space group) and orthorhombic (Pnma) phases coexist, were successfully processed. Highly dense (7.92 g/cm3, 97.5% of the theoretical one) and electrically resistive ( 2.19 × 10 11 Ω ⋅ c m ) nano-structured ceramics with high internal micro-strain levels (up to 1.08%), small crystallite size (24 nm) and elevated magnetization (ranging from 0.204 to 0.350 e m u / g at 15 kOe) with an expressive non-linear response were obtained by combining cryomilling, SPS and oxidative annealing. Particularly, the dielectric response is improved by oxidative annealing at 200 °C, reaching 170 at 1 kHz with very low loss tangent (2.5%). This study demonstrated the effectiveness of the chosen synthesis route in the production of BFO-based ceramics with enhanced ferroic properties.

In this manuscript the multifunctional multiferroic 0.6BiFeO3-0.4PbTiO3 (BFPT) thin films are presented as an interesting alternative for multifunctional photovoltaic applications. The compound is chemically and structurally stable at high temperatures and consequently reliable to work under difficult operating conditions, such as sunlight radiation. Nanostructured single-phased BFPT thin films were processed and their electric, dielectric, structural, and optics properties were characterized in this work. The films were used as active layers in a heterostructured photovoltaic arrangement, which proves their photovoltaic behavior. Interesting physical properties, as intrinsic photovoltage production (~ 1 mV/cm2) with excitation power (300 W) were associated to the high dielectric constant (> 220 at 1 kHz and room temperature), the existence of long-range electrical conductivity processes, and the presence of two band gap energies (at 3.95 eV and 2.51 eV) in the BFPT compound that enhance the light absorption with consequent photovoltaic generation in the visible light region.

A novel lead-free Ba(1-x)(La,Na)xTiO3 (BLNT), (0 ≤ x ≤ 0.08) ferroelectric ceramic with enhanced energy storage density was fabricated by the conventional solid-state method. With an increase in La...

The dynamics of ferroelectrics domain walls is modeled by the equation of a particle in a force field. It is considered that over the domain walls act the forces due to the interaction with an exte...

Narrowing the bandgap energy of perovskite ferroelectrics is a potential task for improving PV applications. This study examined the effect of Ni2+/Na+ co-substitution on the structural, optical, electrical, and magnetic properties of Ba1-x(Nix/2,Nax)TiO3 (BTNaNi-x) ceramics, where (0 ≤ x ≤ 0.08), prepared by solid-state reaction method. X-ray diffraction along with structure refinement verifies the existence of perovskite structure with a tetragonal phase in all samples. The morphological study reveals a non-uniform grain size distribution with a decrease in grain size with an increase in co-substitution concentration. XPS study gives direct evidence of oxygen vacancies in the investigated sample. The oxygen vacancies and octahedral distortion accompanying the Ni2+/Na+ co-substitution significantly reduce the optical bandgap of BaTiO3 ceramics from 3.14 to 2.688 eV. The temperature dependence of the dielectric constant is measured in the range of 30–250 °C at the frequency of 1 kHz. The results reveal that the transition temperature gradually decreased with an increase in Ni2+ and Na+ concentrations. This phenomenon was interpreted based on reducing grain size and tetragonality with co-substitution. The ferroelectric and magnetic properties are determined by (P–E) and (M–H) hysteresis loops at room temperature. Magnetic properties are significantly enhanced with an increase in the Ni2+, Na+ contents in the system. The correlation between the ESR width parameter (ΔH) and asymmetry parameter (Pays) with concentrations (x) reveals that the sample with x = 0.08 has a strong magnetic nature compared to other samples.

Real-time tuning of photoluminescence properties are highly desirable for potential applications. Thus, one proposed approach is to tune the photoluminescence emissions by applying an external electric field. However, in order to switch the ferroelectric polarization, high quality bulk ceramics is demanded. In this work, soft and hard Er3+-doped (K,Na)NbO3 piezophotonic ceramics were prepared by the conventional route and their microstructural, structural and up-conversion emission properties were investigated. Dense and free from secondary phases ceramics were successfully produced. The photoluminescence spectra, in the visible range, were characterized as a function of the pumping power. For the soft composition, a remarkable green shift was verified with increasing the laser power. It was supposed that the excited state absorption, involving a three-photon absorption process, was involved in the 4S3/2→4I15/2 transition. For the hard composition, the two-photon absorption process was dominant and the presence of complex defects reduced significantly the 4F9/2→4I15/2 transition.

The influence of sintering temperature on the optical properties of (K0.8Ba0.2)(Nb0.9Ni0.1)O3-δ (KBNNO) and Pb(Ti0.9Ni0.1)O3-δ (PTNi) ceramics was investigated. It was found that by increasing the ...

Cu-doped sodium potassium niobate single crystal fibers (KNN-Cu) were grown by the micro-pulling-down technique under different atmospheres, namely, argon, synthetic air and oxygen. The str...

In this work the photovoltaic response of ferroelectric Pb(Zr0.20Ti0.80)O3 (PZT) thin films, with asymmetric Metal/Ferroelectric/Metal structure (Au/PZT/ITO), was investigated and its effect correl...

The effects ytterbium doping on the structure, microstructure, and dielectric properties of 0.86PbMg1/3Nb2/3O3+0.13PbTiO3+0.01La2O3+xYb2O3 were studied (x=0.5, 1.0, 1.5 and 2.0 mol%). The ceramics ...

In this work, (K0.48Na0.52)NbO3 (KNN) ceramics were prepared by using Spark Plasma Sintering (SPS) method applying different heating rates. The microstructural evolution of the ceramics was analyze...

The influence of hot forging temperature on microstructure and magnetoelectric properties in (0.8)Pb(Mg1/3Nb2/3)0.68Ti0.32O3+(0.2) NiFe2O4 particulate composites were investigated. Samples sintered...

In this manuscript, microstructural, structural and magnetic properties of pure and La doped (0.6)BiFeO3-(0.4)PbTiO3 polycrystals were investigated. X-ray diffraction, transmission and scan...

Since the discovery of an effective role for defects in improving the performance of ceramic materials in practical application, investigation of defects and their impact on the development of optical properties in condensed matter physics have received widespread attention. In this work we synthesized a lead free (Ba0·60Sr0.40)(1-x)(Bi,Li)xTiO3 (BST6:BLx%); (0%≤x ≤ 8%) ceramics using a conventional solid-state reaction method. X-ray diffraction patterns along with Rietveld refinement, Micro-Raman (MR) spectroscopy, X-ray Photoelectron Spectroscopy (XPS), UV–visible, Electron Spin Resonance (ESR) and photoluminescence (PL) measurements are utilized to characterize these ceramics. XRD, and Raman analysis have proven cubic phase symmetry with a contraction in bond length as the Bi and Li concentrations increased. XPS and ESR results confirm the presence of Ti3+ surface defects (TSD) and oxygen vacancies (VO) on the co-substituted samples sintered at high temperature. The optical results show a decrease in the bandgap energy from 3.14 eV to 2.76 eV and a wide-PL band emission on the green band, caused by recombination of the radiative free electrons and holes trapped around the surface oxygen vacancies. Defect levels created within the bandgap might act as recombination centres, and this can give the possibility of using BST6:BLx as a green light emission source in future practical applications.

In this work, combining macroscopic and nanoscopic analyses, we explored the role of domain structure and relative domain-electric field orientations in the polarization reorientation process in polycrystalline ferroelectric thin films. Results of macroscopic ferroelectric and dielectric measurements were interpreted considering a detailed characterization of the domain structure, performed by piezoresponse force microscopy (PFM). A phenomenological model was utilized to obtain macroscopic parameters related to the polarization reorientation, domain structure, and domain wall mobility. We investigated tetragonal Pb(Zr, Ti)O3 (PZT) thin films with preferential in-plane polarization ([100] direction) and mixed in-plane and out of plane polarization ([100] and 〈110〉 directions). Results revealed similar domain structures for the films, consisting of a high density of stripe domains, with a width of 10 – 15 nm, separated by 90∘ walls. With the application of an electric field, such a structure is rearranged but maintained a high density of 90∘ walls after removing the field. Combining the macroscopic and nanoscopic analyses, we found that the relative polarization orientation of the domains significantly impacts the reorientation process. For the [100] oriented film, the reorientation occurs mainly by the rotation of a-domains. For these films, the c-domain configuration is very unstable, resulting in a high backswitching of the polarization after removing the field. On the other side, the increase of the 〈110〉 film orientation represents an increase of domains with the out-of-plane component of polarization that can reorient by 180∘ or 90∘ switching and stabilize. This results in a more abrupt reorientation process and a reduction of the backswitching effect. The parameters obtained with the phenomenological model are in good agreement with the response observed by PFM and better explain the macroscopic measurements.

Lead zinc niobate (PZN) and lead titanate (PT) solid solutions close to the morphotropic phase boundary (MPB) exhibit unusually large dielectric and piezoelectric constants. PZN-PT ceramics with a composition close to the MPB processed by the conventional route yield ceramics with a pyrochlore structure. In the last few decades, attempts to synthesize PZN-PT powders with perovskite structure via traditional ceramic methods and novel chemical processing routes have failed. In the present research, an analysis was made of the effect of the calcination atmosphere on the formation of perovskite phase in PZN-10PT powders. To this end, thermal analyses were carried out in four different atmospheres: oxygen, air, argon and nitrogen. The powders were calcined at the temperatures at which the DTA curves presented peaks, and the resulting phases were identified by X-ray diffraction.

Made available in DSpace on 2020-12-12T02:03:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-02-17 The intrinsic contribution of dielectric permittivity was obtained in thin films of PZT pyrolyzed at different temperatures. Pyrochlore phases were observed in films pyrolyzed at temperatures above 350 °C, while only the perovskite phase grows in films pyrolyzed at temperatures lower than 300 °C. Dielectric and ferroelectric properties were characterized, and their behaviors were related to pyrolysis temperature. The dielectric permittivity dependence on the bias electric field was investigated at room temperature for different PZT thin films, and these curves were used to reconstruct the hysteresis loops. In this work, a model was used to reconstruct the hysteretic behavior of the films. The experimental results are in excellent agreement with the applied model. Universidade Federal do Tocantins Departamento de Física e Química Faculdade de Engenharia de Ilha Solteira Universidade Estadual Paulista–UNESP Grupo de Materiais Ferroicos. Departamento de Física Universidade Federal de São Carlos Departamento de Física e Química Faculdade de Engenharia de Ilha Solteira Universidade Estadual Paulista–UNESP

Preventing the formation of the pyrochlore phase in the synthesis of PZN-PT powders requires controlling calcination parameters such as temperature, soaking time and atmosphere. These parameters were examined extensively to determine the time and temperature at which the perovskite phase is the majority phase, as well as the atmosphere that facilitates the formation of this phase. A maximum of 74% of perovskite phase was obtained under the following conditions: 1000 °C, 4 h in nitrogen atmosphere. In this work, we studied the influence of these parameters, which were optimized, on the formation the perovskite phase in PZN-10PT powders synthesized by the conventional solid state method.

In this work, the influence of the grain coarsening on dielectric, magnetic and magnetoelectric properties of particulate composites constituted by (0.8)0.675(Pb(Mg 1/3 Nb 2/3 )O 3 )–0.325PbTiO 2 – (0.2)CoFe 2 O 4 (or PMNPT-CFO) and prepared by solid-state reaction method are presented. The increase of average grain size enhances the tetragonal distortion at the structure of the PMNPT matrix due to control of internal stress of the ferroelectric phase. As consequence, the values of the e′, g 33 and α ME coefficients reached maximum (e′ = 25,000, g 33 = 53 × 10 −4 Vm/N and α ME = 14.5 mV/cm Oe) as result of the enhancement of domain structure in the composites. An increase of aprox. 65% in the magnetoeletric coefficient was achieved controlling the microstructure of composites indicating that the magnetoelectric properties in these composites systems could be enhanced by the correct control of the grain coarsening between the phases in particulate composites.

In this paper, a quantification of the polar/non-polar phases of perovskite single-phase relaxor ferroelectric ceramics of lanthanum modified lead titanate zirconate (PLZT x/65/35, x = 5, 8, 9 and 10%) was performed by Rietveld refinement using measurements obtained with Cu kα radiation and with high-resolution synchrotron radiation. The refinements were performed concerning two crystalline phases, being one of them nonpolar (Pm-3m) and the other polar. The refinement results showed the relationship between the polar/nonpolar phases and the La content in PLZT, suggesting the existence of polar clusters of relaxor ferroelectric ceramics.

This work uses the electromechanical resonance technique to investigate the piezoelectric properties of Pb0.55Ca0.45TiO3 ceramics as a function of temperature. The elastic compliance coefficient, s11E, and the transverse electromechanical coupling factor, k31, were calculated based on the harmonic oscillator model of piezoelectric vibrating sample. In addition to the analysis of the temperature dependence of the piezoelectric response, the thermal depoling current and the real and imaginary parts of the dielectric permittivity as a function of the temperature were investigated. The thermal stability of the piezoelectric response was determined and the non-accordance of the temperature anomalies of k31, s11E, dielectric and pyroelectric coefficients were discussed.

The influence of ferromagnetic phase properties on the magnetoelectric response of hot pressed particulate composites formed by 80 mol% of 0.675[Pb(Mg1/3Nb2/3)O3]–0.325[PbTiO3] as piezoelectric matrix and 20 mol% of NiFe2O4, CoFe2O4 or BaFe12O19 phases was analyzed. The hot pressing sintering method was suitable for obtaining composites with apparent density higher than 94% and electric resistivity close to 109 Ω.m, independently of the ferromagnetic phases used. The magnitude of the magnetoelectric coupling seems to be governed by the piezoelectric properties of ferroelectric PMN-PT matrix, and the zero bias magnetoelectric coefficient values are determined by the ferromagnetic hardness of the magnetic phase.

This paper reports the electric, magnetic and magnetoelectric properties of particulate composites of the system with ferroelectric phase 0.675[Pb(Mg1/3Nb2/3)O3]−0.325[PbTiO3] and magnetic phase CoFe2O4 prepared by Spark Plasma Sintering technique. Optimized sintering and thermal annealing parameters were applied in order to achieve highly dense microstructure with sub micrometric grain size distribution for both phases. The results from the dielectric measurements showed a diffuse and dispersive phase transition. P-E and M-H loops revealed the simultaneous existence of ferroelectric and ferrimagnetic ordering, respectively. Moreover, at cryogenic temperatures an anomalous behavior on the bias magnetic field dependence was observed for the magnetoelectric voltage coefficient.

Nanostructured Pb(Fe1/2Nb1/2)O3 (PFN) ceramics were synthesized by an innovative processing route, which involves micro-milling and spark plasma sintering (SPS). This procedure allows obtaining samples with high densities and minimal grain growth. In this sense, the parameters involved during the SPS procedure and the sintering mechanisms were considered. It became evident that the pulsed dc electric current, high heating rates and simultaneous application of pressure improved the transport mechanisms responsible for shrinkage and densification, making it possible to lower the sintering temperature and thereby avoid the grain growth that occurs in conventional sintering.

Piezoelectric transformers are devices able to raise an electrical input voltage with low energy losses. However, there are a few reports on the designing of multiferroic piezoelectric transformers. In this paper, an alternative bi-layer radial mode piezoelectric/magnetoelectric transformer approach by using a Nb doped (1 wt%) Pb(Zr)53Ti47O3 piezoelectric ceramic as actuator, and a La doped (5 wt%) (0.6)BiFeO3-(0.4)PbTiO3 magnetoelectric ceramic as transducer has been tested. The voltage gain and the efficiency were determined as a function of the frequency and the load test resistance. A typical response, characteristic of bi-layered radial mode solid-state transformer, with a voltage gain of 2.5 at a load resistance of 7 kΩ, and an efficiency of 0.15 at load resistance 1 kΩ, were obtained. The results showed the feasibility of such multiferroic transformer for some practical smart and multifunctional devices applications.

In this work, “pure” and doped (K0.48 Na0.52)NbO3 ceramics (KNN) were prepared by using Spark Plasma Sintering (SPS) method. In order to investigate the influence of doping elements on the microstructural, structural and dielectric properties of KNN, Cu2+ and Li1+ doping elements were added. The results revealed the viability to produce highly dense “pure” and doped KNN ceramics with good crystallization in the perovskite phase. Densities around 96% and 99% of the theoretical one were reached. In relation to pure KNN, it was verified that Cu2+ addition reduced significantly the sintering temperature, revealing a better microstructure with a more homogeneous grain size distribution and structure with well-defined splitting of the XRD peaks. In comparison to pure KNN, the addition of both doping elements decreased both the dielectric constant the dielectric losses as well.

In this work, the influence of the ferroelectric phase on the magnetoelectric response of particulate magnetoelectric composites were investigated. The composites constituted by PMN-PT, PZT and PBN as ferroelectric phase and CoFe2O4 as ferromagnetic phase (prepared through the conventional solid state method) were synthesized by hot forging method in the 80/20 molar ratio using the 0-3 connectivity. We show that the increase in the magnetic coercive field for composites composed by PZT and PBN in comparison to the PMN–PT ferroelectric phase is related to the different elastic constants of ferroelectric matrix used. Also, the ME properties has been attributed to the mechanically mediated effect, in which the ME values are strongly dependent to the piezoelectric and elastic properties of the ferroelectric phases and the maximization of ME coefficient was obtained using ferroelectric and ferromagnetic phases with similar elastic modulus.

The development of energy storage devices in lead-free perovskite materials is critically important in addressing the environmental issues of perovskite lead. In this article, for the first time, lead-free (Ba0.60Sr0.40)(1−x)(Bi,Li) x TiO3, abbreviated as (BST6:BLx%); (0%⩽ x ⩽ 8%) ceramics, have been successively synthesized via the conventional solid-state reaction method. The structural evolution, dielectric and energy storage properties, as functions of co-doping levels, were systematically studied by x-ray diffraction, x-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy, scanning electron microscopy, impedance analyzer, and a Radiant Precision Premier II Analyzer. It was found that a small amount of co-dopants induced a colossal permittivity (CP) (over 105) with low loss (−3 with a BDS of ∼100 kV cm−1, and an efficiency of over 90%. The defects and chemical state of the elements contained in the material’s surface were investigated using XPS. In conjunction with the results of XPS and complex impedance studies, the mechanism of massive permittivity was interpreted based on a defect-dipole model. We believe that BST6:BLx% ceramics, as CP and high energy storage efficiency materials, might be considered a promising candidate for high energy storage applications.

A wide bandgap is one of the greatest issues that restrain the photoelectric application of classical ferroelectric oxides in the visible spectrum. Typical approaches to reduce their bandgap, as well as to tune other physical properties (dielectric, piezoelectric …), is to use specific dopants. This work reports the variation by doping of the structural and optical bandgap properties of the Ba0.92Bi0.04Na0.04Ti0.96M0.04O3 (BNBT-M); (M = Ni, Fe, Co) ceramics. Structural refinement shows that all samples are crystallized with a tetragonal phase with a P4mm space group. Detailed analysis of the bond lengths, bond angles, octahedral distortions demonstrates the cooperative effect induced by the Co, Fe, and Ni doping. UV–Vis absorption spectra showed a decrease in the bandgap and increased absorption for longer wavelengths, induced by transitions metal (TM) ions doping. The bandgap narrowing is attributed to the development of new M − O bonds and states in the electronic structure, as the TM ions are incorporated on the Ti site, with simultaneous oxygen vacancies creation. The formation of oxygen vacancies via metal ions doping in BNBT was proven by ESR study. The present investigation can provide useful insight into the understanding and ferroelectrics bandgap tuning for visible-light photovoltaic applications.

In this work, the relationship between dielectric, ferroelectric, piezoelectric properties and the magnetoelectric coupling in (1-x)PMN-PT/xCFO multiferroic particulate composites were investigated. The magnetodielectric response showed strong frequency and CFO concentration dependence, which for composites with CFO concentration higher than 30 M%, it was reported a magnetodielectric response up to 10% around the electromechanical resonance regime for magnetic fields of 15 kOe. Additionally, at low magnetic fields a positive magnetodielectric coefficient (∼2%) associated to the magnetoelectric coupling was observed. The MD effects for particulate composites were attributed to the co-contribution of the magnetoelectric polarization, at low magnetic fields, and a compressive stress on ferroelectric phase due to magnetostriction effect, at high magnetic field.

In this work, the fabrication of BaFe12O19 (BaM) thin films by radio-frequency sputtering and the influence of substrate orientation on structural, microstructure and magnetic properties were carried out. Measurements pointed out the deposition time and power have no significant effect over stoichiometry in the studied condition, producing films with satisfying Fe:Ba rate confirmed by EDX analysis. The orientation of the Si substrate showed to be essentially correlated with in-plane orientation of BaM phase. Both Si (1 0 0) and (1 1 1) substrates privileged in-plane orientation of the c-axis of BaM and atomic force microscopy found needle-like grains spread randomly onto substrates, although Si (1 1 1) substrate exhibited higher magnetic anisotropy.

In this work, the ferroelectric domain structure of (Pb0.79La0.21)TiO3 transparent ceramics and its response to an applied electric field were investigated by piezoresponse force microscopy (PFM). A qualitative three-dimensional reconstruction of the domains by PFM measurements revealed that the domain structure consists in stripes in two size scales (micro and nanometer) separated by 90° domain walls coexisting with 180° domains. While the nanoscale 90° domains were found arranged in organized structures, (e.g., lamellas, herringbones, and other unusual configurations), the 180° domains form a “labyrinth” structure, typical of ferroelectrics with a degree of disorder. Local application of an electric field reveals different coercive voltages to reorient 180° and the two types of 90° domains and the appearance of a different nanoscale 90° domain structure after poling. While the labyrinth structure is destroyed with relative low voltages, the created 90° domains structure persists, avoiding the formation of a single-domain structure.

Magnetic, electric and mechanical properties can be strongly coupled in multiferroic materials. However, only few models were developed to describe electro-magneto-mechanical coupling effects on them. We report the influence of the strain induced phase transitions on the enhancement of the magnetoelectric intrinsic properties in multiferroic Pb[(Fe2/3W1/3)(1-x)Tix]O3 (x = 0.17,0.20) ceramics. We argue that when both ferroelectric and antiferromagnetic transitions temperatures are closer together, the magnetoelectric intrinsic and extrinsic responses increase. Colossal magnetoelectric intrinsic response was found for Pb(Fe2/3W1/3)0.83Ti0.17O3.

The thermal evolution of the electric field-induced birefringence, δ(Δn(E)) vs T, obtained by the Kerr and Pockels electro-optical effects, was characterized in the La-doped Pb(Mg1/3Nb2/3)O3 – PbTiO3 ferroelectric relaxor ceramic system. The measurements were conducted over a broad temperature range (from 100 K to 650 K), using the dynamic Senarmont compensator method. Moreover, through a particular approach to the analysis of both electro-optical effects as a function of temperature, it was possible to determine the characteristic temperatures predicted for the transitions between the paraelectric (PE), ergodic ferroelectric relaxor (EFR), nonergodic ferroelectric relaxor (NEFR), and normal ferroelectric (FE) states of this system.

Li doped TiO2 rutile-type (TL) polycrystalline ceramics with Li concentration in the range 0≤x≤0.02 have been synthesized by a solid state reaction method. The structural properties were investigated using an x-ray diffraction (XRD) technique. The dc conductivity (σdc), obtained from impedance spectroscopy, has been investigated over the temperature range of 400–750 °C. The activation energy (Ea) of the samples was calculated from the absolute temperature dependence of the dc conductivity. The physical parameters, such as the lattice parameters, dc conductivity and activation energy, show changes in their behavior with increasing Li concentration. Such observed behaviors can be interpreted in terms of two different defect reaction mechanisms. For instance, for x≤0.01 the Li incorporates into interstitial sites, whereas for higher concentrations (0.01

This paper reports on a multi-edge X-ray absorption analysis to elucidate how the substitution of Ti4+ by Zr4+ ions acts on the local order structure and on the O 2p hybridization states of Ba0.9Ca0.1Ti1_xZrxO3 (BCZT) lead-free ceramic compounds, inducing a ferroelectric evolution from a normal to a relaxor character. Ti, Ba, Zr and O X-ray absorption spectra were measured to probe the local and electronic structure of BCZT samples that exhibit a normal (x < 0.18) or relaxor (xP 0.18) ferroelectric character. X-ray absorption near edge structure results show that the local symmetry and distortion of TiO6, ZrO6 and BaO12 units are not significantly affected by the Ti/Zr ratio, the ferroelectric character or the long-range order symmetry. The assignment of the ab initio density of states associated with the O K-edge enabled a correlation between the decrease in the hybridization between O 2p and Ti 3d states and the ferroelectric character evolution of the BCZT samples. The hybridization states in the ferroelectric relaxor samples exhibit a more symmetric spatial configuration, as occurs with long-range symmetry.

The co-existence of ferroelectric and ferromagnetic properties at room temperature is very rarely observed. In multiferroics, microscopic coupling interaction between the ferroelectric and magnetic order results in the macroscopic correlation between the dielectric and magnetic properties, which is defined as magnetodielectric effect. In this paper, the magnetic behavior of the Pb(Fe1/2Nb1/2)O3 ceramics at high temperature has been extensively studied, showing that PFN exhibits ferroelectric and ferromagnetic ordering at room temperature, converting ferroelectric PFN into a multiferroic material at this temperature.

Nanostructured orthorhombic TbMnO 3 polycrystals were synthesized by high-energy ball milling and annealing in Ar or O 2 atmospheres. Oxygen annealed samples show shrunken unit cells in comparison with Ar annealed ones, without Mn valence changes in both cases. Magnetic and dielectric investigations show strong evidence of long-range (43 K) and quasi-long-range (9 K) ordering for Mn and Tb ions, respectively, and a noncollinear spin-spiral magnetic ordering of Mn spins, with higher magnetic response and ferroelectric state for argon synthesized samples.

In this work, high dense, single phase ceramics of the 0.3BiFeO3 0.7BaTiO3 multiferroic solid solution were prepared by spark plasma sintering. The structural, microstructural, multiferroic and piezoelectric properties were investigated. The samples presented good magnetic and ferroelectric properties, Pr = 8.3 μC/cm2 and Mr = 0.03 emu/g, with low dielectric AC losses below the ferroelectric transition temperature. The obtained piezoelectric coefficients were determined as d31 = -8.1 pm/V and d33 = 13.5 pm/V.

Monocristales de ( (1 - x)Pb(Zn1=3Nb2=3)O3-xPbTiO3-PZN-xPT ) con estructura perovskita, muestran excelentes propiedades dieléctricas, ópticas y electrostrictivas en composiciones cerca al contorno de fase morfotrópico (CFM), x 0;09. La preparación de cerámicas con composiciones cercanas al CFM por métodos convencionales, conduce a cerámicas con estructura pirocloro. En este trabajo, polvos de ((1 - x)Pb(Zn1=3Nb2=3)O3-xPbTiO3-PZN-xPT) con x = 0;10 fueron sintetizados por el método de reacción por combustión. Como combustibles fueron usados: CO(NH2)2, C2H5NO2, CO(NH2)2=C2H5NO2 y C4H16N6O2. El resultado indica que el mayor porcentaje de fase perovskita (70 %) fue obtenido usando CO(NH2)2= C2H5NO2 (razón 50=50). Esta fase es mantenida al sinterizar la muestra a 1000 C en atmósfera de nitrógeno. MSC: 74E15, 74E40, 74N15 PACS: 80.81

Multiferroics are interesting materials which present more than one ferroic property and have a great potential for practical applications [,,]. In addition, the coupling of magnetic and electric properties, the magnetoelectric effect (ME), offers news possibilities to applications [2,]. The magnetoelectric effect can be observed in single-phase materials like LuFe2O4, BiFeO3, etc. [1,] or in composites like PMN-PT/CFO, BaTiO3/CoFe2O4, etc. The ME composites have advantages over single-phase materials. They are easier to fabricate, less expensive, and have a wider range of working temperatures than single-phase materials []. However, some parameters that enhance the ME response need to be optimized. These parameters are the composition, the microstructure (grain size, grain orientation) and sintering parameters [6]. Thus, this work attempts to create a synthesis protocol to prepare the ME composite PMN-PT/CFO by Spark Plasma Sintering (SPS) keeping the average grain size as small as possible.