Features of diffuse phase transition in lead barium niobate ferroelectric ceramics

Abstract

Features of the diffuse phase transition in lead barium niobate (PbxBa1−xNb2O6–PBN) ferroelectric ceramics are presented and discussed. Ceramics were prepared near to the morphotropic phase boundary (x∼0.63) and the dielectric properties were investigated. The character of the ferroelectric phase transition was carefully analyzed, indicating that the diffuseness coefficient decreases as the lead concentration increases. This effect is attributed to the increase of the unit-cell polarization with the morphotropic phase boundary proximity. The polarization enhancement induces the formation and interaction between the polar microregions in PBN samples at temperatures higher than Tm. The appearance of dilatation centers, which act as strong oscillating random-field sources and are naturally created due to the peculiar A-site vacancy distribution in PBN structure, increases the maximum dielectric permittivity by the polarization mobility enhancement. On the other hand, the temperature of maximum dielectric permittivity is decreased due to the action of the random fields.

Dielectric behavior of the PbNb2O6 ferroelectric ceramic in the frequency range of 20Hz to 2GHz

“…Specifically, the temperature dependence of the dielectric permittivity (ε) above its maximum value (ε m ), has been widely studied and reported as an important feature in order to determine the character of the phase transition in ferroelectric materials. 4 To the best of our knowledge, no works focusing the study of the dielectric properties in the PN system in a very wide frequency interval, including the microwave frequencies, have been reported in the literature. The objective of the present work is to investigate the dielectric properties of the PbNb 2 O 6 ferroelectric ceramics in a wide temperature and frequency range, including the high frequency region (radio and microwave frequencies).…”

Dielectric and piezoelectric studies of perovskite–tungsten bronze structured (1−x)PLZT–xPBBiN nanoceramic composites by high-energy mechanical activation technique

“…The trend of T c , tan ı RT and tan ı Tc were continuously decreasing throughout the series whilst ε RT and ε Tc were maximum at x = 0.6 and thereafter decreased. In literature, the dielectric permittivity is higher and the diffused phase transition is lesser when PBN is closer to the morphotrophic phase boundary [22]. In our study, we chose the compositions near morphotrophic phase boundary of perovskite PLZT and tungsten bronze PBBN in order to achieve a combined effect of both distinct structures.…”

Diffuse phase transition and impedance spectroscopy analysis of Ba2.15−x Na0.7+x Nb5−x W x O15 (x = 0.25) ferroelectric ceramic

“…For 1 \ c \ 2, the transition is ''incomplete''. This means that the interaction between nucleating ferroelectric clusters in paraelectric matrix begins far above Tm and plays an important role in its diffusive character [12].…”

“…The diffusive nature of the ferroelectric phase transition can be determined based on the Santos-Eiras phenomenological equation [12]:…”