Seweryn Miga - Academia.edu (original) (raw)

Papers by Seweryn Miga

Ceramics based on lead zirconate-titanate Pb(Zr0.70Ti0.30)O3 (PZT), bismuth manganite (BM) and th... more Ceramics based on lead zirconate-titanate Pb(Zr0.70Ti0.30)O3 (PZT), bismuth manganite (BM) and the composite (1 − x) PZT–x BMwere obtained. A systematic study of linear and nonlinear dielectric susceptibilities temperature and frequency dependences was conducted. A composition-induced crossover in nonlinear dielectric susceptibility was detected. The so-called scaled nonlinear susceptibility, a3, was obtained from experimental values of the real part of the linear and third-order nonlinear dielectric susceptibilities. The value for a3 was negative for low BM content in the whole temperature range specific to discontinuous ferroelectric phase transitions and relaxor behavior. In contradiction, a3 was positive for BM and for the composite with sufficiently high BM content. The positive a3 was attributed to a subsystem of dipoles created by trapped charges. Hopping charge transfer, which is a dominant mechanism for conduction in manganites, is responsible for the positive a3 and for th...

Journal of the European Ceramic Society

Materials, 2020

Polyaniline (PANI) was synthesized chemically with the modified rapid mixing protocol in the pres... more Polyaniline (PANI) was synthesized chemically with the modified rapid mixing protocol in the presence of sulfuric acid of various concentrations. A two-step synthetic procedure was utilized maintaining low-temperature conditions. Application of the modified rapid mixing protocol allowed obtaining a material with local ordering. A higher concentration of acid allowed obtaining a higher yield of the reaction. Structural characterization performed with Fourier-transform infrared (FTIR) analysis showed the vibration bands characteristic of the formation of the emeraldine salt in both products. Ultraviolet–visible light (UV–Vis) spectroscopy was used for the polaronic band and the p–p* band determination. The absorption result served to estimate the average oxidation level of PANI by comparison of the ratio of the absorbance of the polaronic band to that of the π–π* transition. The absorbance ratio index was higher for PANI synthesized in a more acidic solution, which showed a higher dop...

Journal of the American Ceramic Society, 2018

Journal of Electroceramics, 2020

Ceramics based on lead zirconate-titanate Pb(Zr0.70Ti0.30)O3 (PZT), bismuth manganite (BM) and th... more Ceramics based on lead zirconate-titanate Pb(Zr0.70Ti0.30)O3 (PZT), bismuth manganite (BM) and the composite (1 − x) PZT–x BM were obtained. A systematic study of linear and nonlinear dielectric susceptibilities temperature and frequency dependences was conducted. A composition-induced crossover in nonlinear dielectric susceptibility was detected. The so-called scaled nonlinear susceptibility, a3, was obtained from experimental values of the real part of the linear and third-order nonlinear dielectric susceptibilities. The value for a3 was negative for low BM content in the whole temperature range specific to discontinuous ferroelectric phase transitions and relaxor behavior. In contradiction, a3 was positive for BM and for the composite with sufficiently high BM content. The positive a3 was attributed to a subsystem of dipoles created by trapped charges. Hopping charge transfer, which is a dominant mechanism for conduction in manganites, is responsible for the positive a3 and for t...

Applied Physics Letters, 2014

The electric susceptibilities χ1, χ2, and χ3 of BaTi1−xSnxO3 ceramics with 0.175 ≤ x ≤ 0.30 are m... more The electric susceptibilities χ1, χ2, and χ3 of BaTi1−xSnxO3 ceramics with 0.175 ≤ x ≤ 0.30 are measured at 90 ≤ T ≤ 350 K and 37 ≤ f ≤ 106 Hz. Crossover from ferroelectric (x = 0.175) to relaxor behavior (x = 0.30) via coexistence of both (x = 0.25) is indicated by increasing polydispersivity and suppression of χ2 intensity. The relaxor properties are due to weak random fields acting on dipolar Ti4+ clusters in non-polar Sn4+ environment. Upon cooling frustrated interaction between the blocked polar nanoregions yields a cluster glass ground state for x = 0.30 as verified by the dynamic criticality of χ1, χ3, and the scaled non-linear susceptibility a3.

Phase Transitions, 2016

ABSTRACT The results of low-temperature linear and nonlinear susceptibilities, polarization measu... more ABSTRACT The results of low-temperature linear and nonlinear susceptibilities, polarization measurements and the dc electric field dependence of the dielectric properties of the lithium-doped potassium tantalate K1-xLixTaO3, x = 0.034 (KLT-3.4%Li) solid solution are presented. The coexistence of the relaxor-like and ferroelectric behavior and different mechanisms leading to either of them are discussed. The observed ferroelectric phase transition is of the first-order type with temperature hysteresis. This transition is due to the off-center motions of Ta ions in the octahedral environment of oxygen ions. Clusters of Li+ ions produce a relaxor-like behavior and random electric field. This field reduces the depolarization field and allows off-center motions of Ta ions and an appearance of spontaneous polarization.

Ferroelectrics, 2016

ABSTRACT Quenched random fields (RFs) are well-known to be a basic driving force of the peculiar ... more ABSTRACT Quenched random fields (RFs) are well-known to be a basic driving force of the peculiar behavior of relaxor ferroelectrics such as PbMg1/3Nb2/3O3 (PMN), SrxBa1-xNb2O6 (SBN), and BaTi1-xZrxO3 (BTZ), hence, giving rise to strong frequency dispersion of the dielectric response, an apparent lack of macroscopic symmetry breaking at low temperatures, and the formation of polar nanoregions (PNRs) thus creating random ‘domain states’. A fundamental completion of relaxor physics toward a superdipolar cluster glass ground state of the randomly interacting PNRs appears necessary as evidenced by dynamic criticality and non-ergodic aging and rejuvenation processes.

physica status solidi (b), 2016

The results of low‐temperature linear as well as nonlinear and electric susceptibility and polari... more The results of low‐temperature linear as well as nonlinear and electric susceptibility and polarization P measurements of the K1–xLixTaO3, x = 0.01 crystal are presented. A coexistence of two different phases within a temperature range where the glassy state sets in is proposed. In the current work, we have proved the existence of an electric field‐revealed precursor ferroelectric phase without low‐frequency relaxation. With decreasing temperature, the second‐order nonlinear electric susceptibility, , which is proportional to the polarization P, increases from zero at about 40 K to at 4.2 K. This behavior is independent of the frequency of the ac probing electric field, and thus discloses the existence of a newly observed polarization component.

Ceramics International, 2016

Abstract Silver–lithium niobate, Ag1−xLixNbO3, is a promising candidate for lead-free piezoelectr... more Abstract Silver–lithium niobate, Ag1−xLixNbO3, is a promising candidate for lead-free piezoelectrics. Ceramic samples for x equal 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.08 and 0.1 were synthesized by solid state reaction. Room temperature X-ray studies indicate that all samples consist mainly of perovskite phase. Only small amounts of secondary phases, namely Ag2Nb4O11, Ag and LiNbO3, appear. For x≈0.06 the orthorhombic–rhombohedral morphotropic phase boundary is observed. Excellent piezoelectric properties, recently reported for x>0.1, may be the result of proximity of morphotropic phase boundary. Scanning electron microscopy and secondary ion mass spectroscopy investigations suggest that the secondary phases occur chiefly at the grain boundaries. Dielectric measurements, carried out in a wide temperature range, revealed that Ag1−xLixNbO3, for x≤0.05, undergoes the same complex sequence of phase transitions as AgNbO3. On the other hand, for x>0.06, the temperature dependence of dielectric permittivity exhibits only two maxima, related to transitions from the ferroelectric R phase to the antiferroelectric M phase and followed by the paraelectric O phase. The dielectric results obtained confirm the existence of the morphotropic phase boundary.

Phase Transitions, 2014

ABSTRACT Relaxor ferroelectrics such as PbMg1/3Nb2/3O3 (PMN), Sr0.75Ba0.25Nb2O6 (SBN75) and BaTi0... more ABSTRACT Relaxor ferroelectrics such as PbMg1/3Nb2/3O3 (PMN), Sr0.75Ba0.25Nb2O6 (SBN75) and BaTi0.65Zr0.35O3 (BTZ35) are disordered ferroelectric solids, in which polar nanoregions (PNRs) are stabilized on cooling by random electric fields due to either charge or structural disorder prior to their cluster glass transitions at Tg. This two-step process is clearly distinct from conventional (atomic) spin glass transitions. Decisive features of the mesoscopic cluster glass ground states are critical glass dynamics at Tg and stretched exponential relaxation, memory and rejuvenation upon aging below Tg.

The dielectric susceptibility of pure and chromium-doped Sr 0.61 Ba 0.39 Nb 2 O 6 single crystals... more The dielectric susceptibility of pure and chromium-doped Sr 0.61 Ba 0.39 Nb 2 O 6 single crystals reveals an appreciable second-harmonic component 2 along with the usual first-and third-order ones, 1 and 3. It is attributed to irreversible prepoling due to trapping of mobile charge carriers in the first half-cycle of the ac probing field. In agreement with predictions for a biased ferroelectric phase transition, the second-and thirdorder nonlinearity coefficients are observed to minimize at the transition temperature T c .

Review of Scientific Instruments, 2007

A fully automatized alternating current (ac) susceptometer is constructed for simultaneous measur... more A fully automatized alternating current (ac) susceptometer is constructed for simultaneous measurements of the phase resolved complex linear and complex nonlinear ac susceptibilities of lossy and dispersive dielectric materials. This relatively simple setup allows measurements over a wide range of experimental variables, such as ac amplitudes up to 40 V, frequencies from 10−2 to 103 Hz, and temperatures from 100 to 600 K utilizing only current/voltage and analog/digital converters and a personal computer. In contrast with the commonly used analysis of the charge accumulated on a standard capacitor in series with the sample our method is based on the analysis of the current flowing directly through the sample. Absence of any capacitive voltage dividers in the measurement circuit eliminates uncontrolled phase shifts. This is why the instrument provides high quality, nonlinear susceptibility data and in particular appears as a very convenient tool for discrimination between continuous ...

Physical Review B, 2004

Large aging effects, investigated via temporal dependences of the dielectric response, are found ... more Large aging effects, investigated via temporal dependences of the dielectric response, are found to be inherent in the uniaxial ferroelectric relaxor systems SBN: Cr and SBN: Ce. The results are discussed on the basis of domain coarsening and domain-wall pinning effects. Owing to the different charge disorder induced by the Cr 3+ and Ce 3+ dopants, a fundamental difference between both systems is established. While SBN: Ce shows only a weak breaking of ergodicity, the SBN: Cr system experiences true ergodicity breaking.

Physica B: Condensed Matter, 2007

ABSTRACT PbYb1/2Ta1/2O3 single crystals were obtained for the first time. They were grown by the ... more ABSTRACT PbYb1/2Ta1/2O3 single crystals were obtained for the first time. They were grown by the flux method. The PbOPbF2B2O3 system was used as a solvent. Dielectric investigations were carried out in 〈100〉c, 〈110〉c and 〈111〉c pseudocubic directions. These studies pointed to anisotropy of dielectric properties. Frequency-independent ε′(T) and ε″(T) maxima related to the antiferroelectric–paraelectric (AFE—PE) phase transition are observed for all directions at 562K. The frequency-dependent ε′(T) and ε″(T) maxima near 400K related to the ferroelectric (FE)–AFE phase transition are observed only in 〈111〉c direction. The hysteresis loops were observed in this direction only. These results point that ferroelectric relaxor properties appear only in 〈111〉c direction. We propose to consider the ferroelectric phase as ferrielectric one.

Phase Transitions, 2002

ABSTRACT

Journal of the European Ceramic Society, 2014

Silver niobate AgNbO 3 is a promising basic compound for high permittivity microwave dielectrics ... more Silver niobate AgNbO 3 is a promising basic compound for high permittivity microwave dielectrics and lead-free piezoelectrics. Stoichiometric and nonstoichiometric Ag x NbO 2.5+x/2 ceramics were obtained for x equal to 0.95, 0.98, 1.00, 1.02, and 1.05. Scanning electron microscopy and X-ray diffraction studies showed that the homogeneity of the perovskite phase and thus the ceramics quality improved with the increase of x. Dielectric and thermal measurements (DSC) were carried out in wide temperature range. They revealed that the phase transitions become less diffused and shift towards higher temperatures with the increase of silver concentration. These temperature shifts are more significant for the low temperature phase transitions, which are connected with appearance of the polar ferroelectric and antiferroelectric states, than for high temperature transitions related to oxygen octahedra tilts. Influence of silver concentration on interaction between electric dipoles and on stability of polar phases is discussed. A few percent silver excess improve significantly ceramic quality.

Journal of Physics: Condensed Matter, 2002

Piezoelectric properties of Na0.5Bi0.5TiO3 ceramics have been investigated over a broad temperatu... more Piezoelectric properties of Na0.5Bi0.5TiO3 ceramics have been investigated over a broad temperature range using a resonance technique. The thermal behaviours of the piezoelectric tensor coefficients d31, d33 and d15 confirm that there is a distinct phase transformation at 200 °C. For the first time it has been found that a piezoelectric signal connected with the tensor component d33 is observed

Journal of Physics: Condensed Matter, 2008

Extending the framework for multiferroic materials, in which long-range electric and magnetic ord... more Extending the framework for multiferroic materials, in which long-range electric and magnetic orderings coexist, we present a novel 'multiglass' concept, where two different glassy states occur simultaneously. It applies to Sr0.98Mn0.02TiO3 ceramics, where the Mn2+ dopant ions are at the origin of both polar and spin glasses. Spin freezing is initiated at the dipolar glass temperature, Tg≈38 K. Below Tg, both glass phases are independently verified by memory and rejuvenation effects. Strong biquadratic interaction of the Mn2+ spins with the optic soft mode of the incipient ferroelectric host crystal SrTiO3 explains the high spin glass temperature and comparably strong higher order magnetoelectric coupling between the polar and magnetic degrees of freedom.

Journal of Physics: Condensed Matter, 2011

Linear and nonlinear dielectric measurements of AgNbO₃ ceramics and single crystals were carried ... more Linear and nonlinear dielectric measurements of AgNbO₃ ceramics and single crystals were carried out for the M phases (77-673 K). The linear dielectric response is dominated by the contribution of the submillimetre relaxational mode related to the Nb⁵+ ion dynamics (M₂-M₃). On the other hand, nonlinear dielectric χ₃' susceptibility revealed anomalies at three characteristic temperatures: 90, 325 and 448 K. Two later ones are connected with changes of the Nb⁵+ ion dynamics. At T(f) = 448 K a partial freezing of the Nb⁵+ ion displacement to the anti-polar, antiferroelectric array takes place. At 325 K further freezing of Nb and Ag displacements to the polar weak relaxor ferroelectric or dipolar glass transition occurs. This polar state coexists with the ground antiferroelectric one.

Ceramics based on lead zirconate-titanate Pb(Zr0.70Ti0.30)O3 (PZT), bismuth manganite (BM) and th... more Ceramics based on lead zirconate-titanate Pb(Zr0.70Ti0.30)O3 (PZT), bismuth manganite (BM) and the composite (1 − x) PZT–x BMwere obtained. A systematic study of linear and nonlinear dielectric susceptibilities temperature and frequency dependences was conducted. A composition-induced crossover in nonlinear dielectric susceptibility was detected. The so-called scaled nonlinear susceptibility, a3, was obtained from experimental values of the real part of the linear and third-order nonlinear dielectric susceptibilities. The value for a3 was negative for low BM content in the whole temperature range specific to discontinuous ferroelectric phase transitions and relaxor behavior. In contradiction, a3 was positive for BM and for the composite with sufficiently high BM content. The positive a3 was attributed to a subsystem of dipoles created by trapped charges. Hopping charge transfer, which is a dominant mechanism for conduction in manganites, is responsible for the positive a3 and for th...

Journal of the European Ceramic Society

Materials, 2020

Polyaniline (PANI) was synthesized chemically with the modified rapid mixing protocol in the pres... more Polyaniline (PANI) was synthesized chemically with the modified rapid mixing protocol in the presence of sulfuric acid of various concentrations. A two-step synthetic procedure was utilized maintaining low-temperature conditions. Application of the modified rapid mixing protocol allowed obtaining a material with local ordering. A higher concentration of acid allowed obtaining a higher yield of the reaction. Structural characterization performed with Fourier-transform infrared (FTIR) analysis showed the vibration bands characteristic of the formation of the emeraldine salt in both products. Ultraviolet–visible light (UV–Vis) spectroscopy was used for the polaronic band and the p–p* band determination. The absorption result served to estimate the average oxidation level of PANI by comparison of the ratio of the absorbance of the polaronic band to that of the π–π* transition. The absorbance ratio index was higher for PANI synthesized in a more acidic solution, which showed a higher dop...

Journal of the American Ceramic Society, 2018

Journal of Electroceramics, 2020

Ceramics based on lead zirconate-titanate Pb(Zr0.70Ti0.30)O3 (PZT), bismuth manganite (BM) and th... more Ceramics based on lead zirconate-titanate Pb(Zr0.70Ti0.30)O3 (PZT), bismuth manganite (BM) and the composite (1 − x) PZT–x BM were obtained. A systematic study of linear and nonlinear dielectric susceptibilities temperature and frequency dependences was conducted. A composition-induced crossover in nonlinear dielectric susceptibility was detected. The so-called scaled nonlinear susceptibility, a3, was obtained from experimental values of the real part of the linear and third-order nonlinear dielectric susceptibilities. The value for a3 was negative for low BM content in the whole temperature range specific to discontinuous ferroelectric phase transitions and relaxor behavior. In contradiction, a3 was positive for BM and for the composite with sufficiently high BM content. The positive a3 was attributed to a subsystem of dipoles created by trapped charges. Hopping charge transfer, which is a dominant mechanism for conduction in manganites, is responsible for the positive a3 and for t...

Applied Physics Letters, 2014

The electric susceptibilities χ1, χ2, and χ3 of BaTi1−xSnxO3 ceramics with 0.175 ≤ x ≤ 0.30 are m... more The electric susceptibilities χ1, χ2, and χ3 of BaTi1−xSnxO3 ceramics with 0.175 ≤ x ≤ 0.30 are measured at 90 ≤ T ≤ 350 K and 37 ≤ f ≤ 106 Hz. Crossover from ferroelectric (x = 0.175) to relaxor behavior (x = 0.30) via coexistence of both (x = 0.25) is indicated by increasing polydispersivity and suppression of χ2 intensity. The relaxor properties are due to weak random fields acting on dipolar Ti4+ clusters in non-polar Sn4+ environment. Upon cooling frustrated interaction between the blocked polar nanoregions yields a cluster glass ground state for x = 0.30 as verified by the dynamic criticality of χ1, χ3, and the scaled non-linear susceptibility a3.

Phase Transitions, 2016

ABSTRACT The results of low-temperature linear and nonlinear susceptibilities, polarization measu... more ABSTRACT The results of low-temperature linear and nonlinear susceptibilities, polarization measurements and the dc electric field dependence of the dielectric properties of the lithium-doped potassium tantalate K1-xLixTaO3, x = 0.034 (KLT-3.4%Li) solid solution are presented. The coexistence of the relaxor-like and ferroelectric behavior and different mechanisms leading to either of them are discussed. The observed ferroelectric phase transition is of the first-order type with temperature hysteresis. This transition is due to the off-center motions of Ta ions in the octahedral environment of oxygen ions. Clusters of Li+ ions produce a relaxor-like behavior and random electric field. This field reduces the depolarization field and allows off-center motions of Ta ions and an appearance of spontaneous polarization.

Ferroelectrics, 2016

ABSTRACT Quenched random fields (RFs) are well-known to be a basic driving force of the peculiar ... more ABSTRACT Quenched random fields (RFs) are well-known to be a basic driving force of the peculiar behavior of relaxor ferroelectrics such as PbMg1/3Nb2/3O3 (PMN), SrxBa1-xNb2O6 (SBN), and BaTi1-xZrxO3 (BTZ), hence, giving rise to strong frequency dispersion of the dielectric response, an apparent lack of macroscopic symmetry breaking at low temperatures, and the formation of polar nanoregions (PNRs) thus creating random ‘domain states’. A fundamental completion of relaxor physics toward a superdipolar cluster glass ground state of the randomly interacting PNRs appears necessary as evidenced by dynamic criticality and non-ergodic aging and rejuvenation processes.

physica status solidi (b), 2016

The results of low‐temperature linear as well as nonlinear and electric susceptibility and polari... more The results of low‐temperature linear as well as nonlinear and electric susceptibility and polarization P measurements of the K1–xLixTaO3, x = 0.01 crystal are presented. A coexistence of two different phases within a temperature range where the glassy state sets in is proposed. In the current work, we have proved the existence of an electric field‐revealed precursor ferroelectric phase without low‐frequency relaxation. With decreasing temperature, the second‐order nonlinear electric susceptibility, , which is proportional to the polarization P, increases from zero at about 40 K to at 4.2 K. This behavior is independent of the frequency of the ac probing electric field, and thus discloses the existence of a newly observed polarization component.

Ceramics International, 2016

Abstract Silver–lithium niobate, Ag1−xLixNbO3, is a promising candidate for lead-free piezoelectr... more Abstract Silver–lithium niobate, Ag1−xLixNbO3, is a promising candidate for lead-free piezoelectrics. Ceramic samples for x equal 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.08 and 0.1 were synthesized by solid state reaction. Room temperature X-ray studies indicate that all samples consist mainly of perovskite phase. Only small amounts of secondary phases, namely Ag2Nb4O11, Ag and LiNbO3, appear. For x≈0.06 the orthorhombic–rhombohedral morphotropic phase boundary is observed. Excellent piezoelectric properties, recently reported for x>0.1, may be the result of proximity of morphotropic phase boundary. Scanning electron microscopy and secondary ion mass spectroscopy investigations suggest that the secondary phases occur chiefly at the grain boundaries. Dielectric measurements, carried out in a wide temperature range, revealed that Ag1−xLixNbO3, for x≤0.05, undergoes the same complex sequence of phase transitions as AgNbO3. On the other hand, for x>0.06, the temperature dependence of dielectric permittivity exhibits only two maxima, related to transitions from the ferroelectric R phase to the antiferroelectric M phase and followed by the paraelectric O phase. The dielectric results obtained confirm the existence of the morphotropic phase boundary.

Phase Transitions, 2014

ABSTRACT Relaxor ferroelectrics such as PbMg1/3Nb2/3O3 (PMN), Sr0.75Ba0.25Nb2O6 (SBN75) and BaTi0... more ABSTRACT Relaxor ferroelectrics such as PbMg1/3Nb2/3O3 (PMN), Sr0.75Ba0.25Nb2O6 (SBN75) and BaTi0.65Zr0.35O3 (BTZ35) are disordered ferroelectric solids, in which polar nanoregions (PNRs) are stabilized on cooling by random electric fields due to either charge or structural disorder prior to their cluster glass transitions at Tg. This two-step process is clearly distinct from conventional (atomic) spin glass transitions. Decisive features of the mesoscopic cluster glass ground states are critical glass dynamics at Tg and stretched exponential relaxation, memory and rejuvenation upon aging below Tg.

The dielectric susceptibility of pure and chromium-doped Sr 0.61 Ba 0.39 Nb 2 O 6 single crystals... more The dielectric susceptibility of pure and chromium-doped Sr 0.61 Ba 0.39 Nb 2 O 6 single crystals reveals an appreciable second-harmonic component 2 along with the usual first-and third-order ones, 1 and 3. It is attributed to irreversible prepoling due to trapping of mobile charge carriers in the first half-cycle of the ac probing field. In agreement with predictions for a biased ferroelectric phase transition, the second-and thirdorder nonlinearity coefficients are observed to minimize at the transition temperature T c .

Review of Scientific Instruments, 2007

A fully automatized alternating current (ac) susceptometer is constructed for simultaneous measur... more A fully automatized alternating current (ac) susceptometer is constructed for simultaneous measurements of the phase resolved complex linear and complex nonlinear ac susceptibilities of lossy and dispersive dielectric materials. This relatively simple setup allows measurements over a wide range of experimental variables, such as ac amplitudes up to 40 V, frequencies from 10−2 to 103 Hz, and temperatures from 100 to 600 K utilizing only current/voltage and analog/digital converters and a personal computer. In contrast with the commonly used analysis of the charge accumulated on a standard capacitor in series with the sample our method is based on the analysis of the current flowing directly through the sample. Absence of any capacitive voltage dividers in the measurement circuit eliminates uncontrolled phase shifts. This is why the instrument provides high quality, nonlinear susceptibility data and in particular appears as a very convenient tool for discrimination between continuous ...

Physical Review B, 2004

Large aging effects, investigated via temporal dependences of the dielectric response, are found ... more Large aging effects, investigated via temporal dependences of the dielectric response, are found to be inherent in the uniaxial ferroelectric relaxor systems SBN: Cr and SBN: Ce. The results are discussed on the basis of domain coarsening and domain-wall pinning effects. Owing to the different charge disorder induced by the Cr 3+ and Ce 3+ dopants, a fundamental difference between both systems is established. While SBN: Ce shows only a weak breaking of ergodicity, the SBN: Cr system experiences true ergodicity breaking.

Physica B: Condensed Matter, 2007

ABSTRACT PbYb1/2Ta1/2O3 single crystals were obtained for the first time. They were grown by the ... more ABSTRACT PbYb1/2Ta1/2O3 single crystals were obtained for the first time. They were grown by the flux method. The PbOPbF2B2O3 system was used as a solvent. Dielectric investigations were carried out in 〈100〉c, 〈110〉c and 〈111〉c pseudocubic directions. These studies pointed to anisotropy of dielectric properties. Frequency-independent ε′(T) and ε″(T) maxima related to the antiferroelectric–paraelectric (AFE—PE) phase transition are observed for all directions at 562K. The frequency-dependent ε′(T) and ε″(T) maxima near 400K related to the ferroelectric (FE)–AFE phase transition are observed only in 〈111〉c direction. The hysteresis loops were observed in this direction only. These results point that ferroelectric relaxor properties appear only in 〈111〉c direction. We propose to consider the ferroelectric phase as ferrielectric one.

Phase Transitions, 2002

ABSTRACT

Journal of the European Ceramic Society, 2014

Silver niobate AgNbO 3 is a promising basic compound for high permittivity microwave dielectrics ... more Silver niobate AgNbO 3 is a promising basic compound for high permittivity microwave dielectrics and lead-free piezoelectrics. Stoichiometric and nonstoichiometric Ag x NbO 2.5+x/2 ceramics were obtained for x equal to 0.95, 0.98, 1.00, 1.02, and 1.05. Scanning electron microscopy and X-ray diffraction studies showed that the homogeneity of the perovskite phase and thus the ceramics quality improved with the increase of x. Dielectric and thermal measurements (DSC) were carried out in wide temperature range. They revealed that the phase transitions become less diffused and shift towards higher temperatures with the increase of silver concentration. These temperature shifts are more significant for the low temperature phase transitions, which are connected with appearance of the polar ferroelectric and antiferroelectric states, than for high temperature transitions related to oxygen octahedra tilts. Influence of silver concentration on interaction between electric dipoles and on stability of polar phases is discussed. A few percent silver excess improve significantly ceramic quality.

Journal of Physics: Condensed Matter, 2002

Piezoelectric properties of Na0.5Bi0.5TiO3 ceramics have been investigated over a broad temperatu... more Piezoelectric properties of Na0.5Bi0.5TiO3 ceramics have been investigated over a broad temperature range using a resonance technique. The thermal behaviours of the piezoelectric tensor coefficients d31, d33 and d15 confirm that there is a distinct phase transformation at 200 °C. For the first time it has been found that a piezoelectric signal connected with the tensor component d33 is observed

Journal of Physics: Condensed Matter, 2008

Extending the framework for multiferroic materials, in which long-range electric and magnetic ord... more Extending the framework for multiferroic materials, in which long-range electric and magnetic orderings coexist, we present a novel 'multiglass' concept, where two different glassy states occur simultaneously. It applies to Sr0.98Mn0.02TiO3 ceramics, where the Mn2+ dopant ions are at the origin of both polar and spin glasses. Spin freezing is initiated at the dipolar glass temperature, Tg≈38 K. Below Tg, both glass phases are independently verified by memory and rejuvenation effects. Strong biquadratic interaction of the Mn2+ spins with the optic soft mode of the incipient ferroelectric host crystal SrTiO3 explains the high spin glass temperature and comparably strong higher order magnetoelectric coupling between the polar and magnetic degrees of freedom.

Journal of Physics: Condensed Matter, 2011

Linear and nonlinear dielectric measurements of AgNbO₃ ceramics and single crystals were carried ... more Linear and nonlinear dielectric measurements of AgNbO₃ ceramics and single crystals were carried out for the M phases (77-673 K). The linear dielectric response is dominated by the contribution of the submillimetre relaxational mode related to the Nb⁵+ ion dynamics (M₂-M₃). On the other hand, nonlinear dielectric χ₃' susceptibility revealed anomalies at three characteristic temperatures: 90, 325 and 448 K. Two later ones are connected with changes of the Nb⁵+ ion dynamics. At T(f) = 448 K a partial freezing of the Nb⁵+ ion displacement to the anti-polar, antiferroelectric array takes place. At 325 K further freezing of Nb and Ag displacements to the polar weak relaxor ferroelectric or dipolar glass transition occurs. This polar state coexists with the ground antiferroelectric one.