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In this work, we report on the results of the examination of the nonlinear dielectric response of layered ferrielectic CuInP2S6 and Cu0.9Ag0.1InP2S6 crystals. The temperature behaviour of the nonlinear dielectric properties of ferrielectic CuInP2S6 and Cu0.9Ag0.1InP2S6 is found to be consistent with Landau theory. The additional peak of the third-order nonlinear susceptibility in these crystals, below the phase transition temperature, is strongly influenced by the electric field amplitude, and it is caused by the ferroelectric domain dynamics. The nonzero value of the second-order susceptibility and the mismatch between the temperatures of linear and third-order susceptibilities indicate that some polarisation exists above the phase transition temperature. [ABSTRACT FROM AUTHOR]

Ceramics of the perovskite multiferroics PbFe0.5Nb0.5O3 (PFN) and PbFe0.5Ta0.5O3 (PFT) were synthesized from new citrate polymeric precursors. X‐ray tests pointed to trace amounts of the pyrochlore phase. SEM studies revealed the heterogeneous grain size distribution for PFN and the homogeneous one for PFT. Dielectric studies pointed to one diffuse T‐C phase transition at 378 K for PFN and two diffuse M‐T and T‐C phase transitions, at 200 and 235 K, for PFT, respectively. X‐ray photoelectron spectroscopy studies of PFN reveal that all ions exist in one valence state, however, with two chemical shifts for Pb2+. Two valence states for the majority of ions of PFT seem to be connected with a higher volume fraction of the amorphous grain‐boundary phase. The electronic energy band gap for both compounds is approximately 2.8 eV. Two magnetic transitions, ie, from the paramagnetic to the antiferromagnetic phase and then to the spin‐glass phase, were observed at 156 and 10 K for PFN, and at 145 and 15 K for PFT, respectively. [ABSTRACT FROM AUTHOR]

The results of low-temperature linear [ABSTRACT FROM AUTHOR]

The results of low-temperature linear [ABSTRACT FROM AUTHOR]

The crossover of single crystalline SrxBa1 - xNb2O6 (SBN) from ferroelectric to relaxor behavior when increasing the Sr2+ content from x = 0.4 to x = 0.75 is investigated by dielectric low-frequency susceptometry and scanning piezo-force microscopy. Increasing quenched random electric fields are conjectured to be responsible for the observed increasing dielectric polydispersivity and the growing fractality of the polar 180° domains. A simple statistical model taking into account the varying occupation of the different A-sites with vacancies, Sr2+ and Ba2+ ions, and their influence on the average RF strength is proposed to describe the transformation to the relaxor behavior with increasing x. [ABSTRACT FROM AUTHOR]

Linear and nonlinear dielectric studies of AgNb1-xTaxO3 (ATN) ceramics (x ⩽ 0.6) were carried out in the temperature range of 80 to 673K. The temperature dependences of third-order nonlinear electric susceptibility X3'(T) exhibit two distinct maxima: at the temperature of the weak ferroelectric phase appearance, M1-M2 transition, and at the temperature of the Nb/Ta ion dynamics freezing, Tf. For AgNbO3, they appear at 325K and 448K, respectively. With increasing Ta concentration, both maxima shift toward lower temperature: 4K/%Ta (M1-M2) and 5.6K/%Ta (Tf). The X3' (T) maxima indicate changes of the Nb/Ta ion dynamics and their contribution to electric susceptibility. At Tf, a partial freezing of the Nb/Ta ion displacements to the disordered antipolar, antiferroelectric array takes place. At the M1-M2 transition, further freezing of Nb/Ta displacements to polar weak relaxor ferroelectric or dipolar glass transition occurs. This polar state coexists with the ground antiferroelectric state. Studies of the aging process showed that below Tf the aging influence on electric susceptibility is substantial, whereas above Tf it may be neglected. This means that for ATN ceramics in the concentration range used for applications, there is no aging process in the room temperature region, which is an additional advantage of this system. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we present our measurements of the linear and nonlinear dielectric permittivity of solid solutions (x =0, 0.05, 0.1, 0.15). The dielectric anomaly increases in the system with respect to the concentration of lead, showing that interactions between dipolar entities are modified. The system exhibits dipolar-glass-like behaviour at low values of x ( ). Relaxor behaviour emerges in the sample where . Furthermore, a spontaneous first-order phase transition from relaxor to normal ferroelectric is observed at . A few peculiar dispersion regions are observed in the ferroelectric phase, which we attribute to the coexistence of ferroelectric and dipolar glass phases. On the other hand, the nonlinear dielectric response indicates the existence of compressible polar nanoregions as common elementary dipolar entities in both relaxor and glass-like states. Dielectric spectra were approximated with empirical Cole–Cole or Havriliak–Negami equations. It is shown that the temperature dependencies of mean relaxation times, which were obtained from dielectric spectra, follow the Vogel–Fulcher equation in all samples. Moreover, distributions of relaxation times are obtained and a phase diagram is presented. [Copyright &y& Elsevier]