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Journal ArticleDOI

Dielectric and Raman studies of (BaxPb1−x)(Yb0.5Nb0.5)O3

TL;DR: In this article, Raman spectra of the solid solution series (BaxPb1−x)(Yb0.5Nb 0.5)O3 from x = 0.0 to 0.3 have been analyzed and a new mode at 420 cm−1 is observed for the compounds with Ba2+ substitution.
Abstract: Dielectric dispersion and Raman studies are carried out on the solid solution series (BaxPb1−x)(Yb0.5Nb0.5)O3 from x = 0.0 to 0.3. The x-ray diffraction analysis indicates that with the substitution of Ba2+, the intensity of the peaks corresponding to antiparallel displacement of Pb2+ decreases and the structure becomes cubic. The low frequency dielectric dispersion studies indicate that the series undergoes a transition from an antiferroelectric to a relaxor ferroelectric with variation of x. Raman spectra of the compositions indicate the presence of a greater number of modes for the compounds with cubic structure (). A new mode at 420 cm−1 is observed for the compounds with Ba2+ substitution. The intensity of this mode increases monotonically with increase in Ba2+ substitution and this has been attributed to the commencement of local distortion. This could be responsible for the appearance and increase in the diffuseness around Tmax, the temperature corresponding to .
Citations
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TL;DR: In this paper, the double P-E hysteresis loops of PYNS-xSn ceramics were observed at the temperatures higher than 180°C, confirming its antiferroelectric nature.

6 citations

Journal ArticleDOI
TL;DR: In this article , order-degree-modulated ferroic response and electrocaloric effect (ECE) in Pb(B1,B2)O3-type B-site complex antiferroelectrics are explored.
Abstract: The order-degree-modulated ferroic response and electrocaloric effect (ECE) in Pb(B1,B2)O3-type B-site complex antiferroelectrics (AFEs) are explored in this work. The results show that local/phase structure and dielectric/ferroic properties are strikingly dependent on the degree of order (high, intermediate and low for samples S1, S2 and S3, respectively). A decrease in the content of the AFE orthorhombic phase and an increase in the weakly polar disorder phase is observed from S1 to S3, accompanied by an enhanced relaxation behavior with a smearing of the AFE-to-paraelectric phase transition. Ferroic and EC responses in the three samples present distinct features. Antiferroelectricity wakes-up significantly in sample S1, which boosts the ECE to ∼0.95 K and is almost three times that of S3 (∼0.23 K). An abnormal ECE [negative ECE with a hop–hop character and asymmetrical electrocaloric (EC) response] is unexpectedly found in sample S1. The underlying mechanism is unveiled by dipolar relaxation and phenomenology analysis, which states that the AFE coupling strength dominates the EC performance in this AFE. This work not only presents a refreshing method for order-degree regulation of the ECE in B-site complex AFEs, but also clarifies the possibility that AFEs with robust dipolar coupling strength have an unconventional ECE.
Journal ArticleDOI
TL;DR: In this article, the crystal structure and dielectric properties of Pb1−xCax(Yb0.5Nb 0.5) 1−x(Fe0.6, 0.8, 1.0) have been investigated by X-ray diffraction and Raman spectroscopic measurements.
References
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Journal ArticleDOI
TL;DR: In this paper, it was shown that the degree of order in the B site Sc3+, Ta5+ cations can be controlled by suitable thermal annealing.
Abstract: In Pb(Sc0.5Ta0.5)O3 it has been shown that the degree of order in the B‐site Sc3+, Ta5+ cations can be controlled by suitable thermal annealing. For samples which have been well‐ordered by long annealing, dielectric measurements on single crystals show a normal first‐order ferroelectric phase change at 13 °C and a maximum low‐temperature spontaneous polarization of 23.0 μc/cm2. With increasing disorder, the crystals begin to exhibit the classical diffuse phase transition of a ferroelectric relaxor, with a broad Curie range and strong low‐frequency dielectric dispersion in the transition range. X‐ray diffraction measurements of the size of the ordered microregions suggest that ordering proceeds by different mechanisms in single‐crystal versus ceramic samples, though the resulting effects upon the dielectric behavior are very similar.

769 citations

Journal ArticleDOI
TL;DR: In this paper, the perovskite structure of the relaxor PbMg1/3Nb2/3O3 (PMN) was studied using X-ray and neutron powder diffraction data.
Abstract: The perovskite structure of the relaxor PbMg1/3Nb2/3O3 (PMN) is studied using X-ray and neutron powder diffraction data. The static diffuse scattering (SDS) observed in the diffraction patterns at low temperatures is interpreted using a two-phase Rietveld analysis. The structural model is based on a long-range structure with an average cubic symmetry, and a short-range order due to atomic shifts involved by the formation of polar regions. The two-phase model provides a good improvement in reliability factors. The correlation length and the coexistence of different phases at low temperatures are discussed.

334 citations

Journal ArticleDOI
TL;DR: In this paper, a correlation between the nanoscale B-site order and relaxor on glassy ferroelectric behavior is found in these lead perovskites, and a hypothesis is suggested which relates 0-3 polar connectivity to order-disorder connectivity.
Abstract: From transmission electron microscopy studies on several complex lead perovskite compounds Pb(B'B'')O3, and their solid solutions a classification can be obtained based on B-cation order. This classification divides the complex lead perovskites into three subgroups; random occupation or disordered, nanoscale or short coherent long-range order and long coherent long-range order of B-site cations. A correlation between the nanoscale B-site order and relaxor on glassy ferroelectric behavior is found in these lead perovskites. An hypothesis is suggested which relates 0-3 polar connectivity to 0-3 order-disorder connectivity. This hypothesis is discussed with relation to present theories [G. A. Smolenskii: J. Phys. Soc. Jpn. (1970) Suppl., p. 26, L. E. Cross: Ferroelectrics 76 (1987) 241, T. L. Renieke and K. L. Ngai: Solid State Commun. 18 (1973) 1543] and reported experimental results of the perovskite relaxor ferroelectrics.

319 citations

Journal ArticleDOI
TL;DR: In this paper, a classification of complex lead perovskites is presented based on the relative scale of long-range cation order, and the implications of Cation order in relation to relaxor and normal ferroelectric behavior are discussed.
Abstract: From a number of studies on ferroelectric and related materials based on complex lead perovskites [Pb(Bx′B1−x″)O3], it is apparent that the B-site cation order influences the crystallography, phase transitions, and other physical properties. A classification of complex lead perovskites is presented based on the relative scale of long-range cation order. In particular, we discuss the implications of cation order in relation to relaxor and normal ferroelectric behavior.

317 citations

Journal ArticleDOI
TL;DR: In this article, a zero-field spontaneous relaxor-ferroelectric transition is reported in Pb(Sc 0.5Ta0.5)O3 (PST), with and without defects.
Abstract: A zero-field spontaneous relaxor-ferroelectric transition is reported in Pb(Sc0.5Ta0.5)O3 (PST). This behavior is different from that of other relaxors, where such transitions occur only under the field. A highly disordered PST that has the wide relaxation spectrum typical of relaxors is shown to transform spontaneously into a macroscopic ferroelectric state. Introduction of defects (lead vacancies) into the material impedes the transition resulting in the usual relaxor behavior. Dielectric properties of PST, with and without defects, are analyzed. For the interpretation of the observed properties, a model invoking an additional nonpolar phase is proposed. This model does not imply a freezing in the system. At the low-frequency limit, it is possible to account for the Vogel-Fulcher (VF) law for the temperature of the maximum of the dielectric constant, using only the commonly accepted assumption of an exponentially wide relaxation time spectrum that shrinks on heating. The presented approach interprets the observed proximity between the ferroelectric phase transition temperature and that of the freezing temperature obtained from the VF relation.

274 citations