Dielectric Relaxation Mechanisms in Relaxor Bi-Layered Perovskites

Abstract

Sr_1-xBa_xBi₂Nb₂O₉ (x = 50 and 90 mol%) ferroelectric bi-layered perovskites exhibit a complex dielectric response, showing typical relaxor behavior with strong dispersion of the dielectric permittivity. The Cole-Cole model describes the relaxation processes. Two relaxation processes are analyzed considering: i) the relaxor-like ferroelectric behavior, resulting from the inhomogeneous distribution of barium due to its preference for the bismuth site in the (Bi₂O₂)²⁺ layers, and ii) the interaction between the dipoles, which form the microdomains above the relaxor ferroelectric peak, and the electrons, which are due to the ionization of the oxygen vacancies.

Keywords:

• Bi-layered pervoskites
• dielectric relaxation
• dielectric permittivity

Acknowledgments

The authors want to thank to the ICTP for financial support of Latin-American Network of Ferroelectric Materials. Special thanks to Dr. E. B. Araújo (Universidade Estadual Paulista, Ilha Solteira, SP—Brazil) and Dr. A. Franco Júnior (Universidade Federal de Goiás, Goiânia, GO—Brazil).