High-Temperature Dielectric Relaxation and Electric Conduction Mechanisms in a LaCoO₃-Modified Na_0.5Bi_0.5TiO₃ System

Abstract

This research study examines the high-temperature dielectric relaxation and electric conduction mechanisms in (<i>x</i>)LaCoO₃-(1 - <i>x</i>)Na_0.5Bi_0.5TiO₃ samples, where <i>x</i> is 0.05, 0.10, and 0.15. The findings demonstrate that all the samples exhibit two dielectric transitions: first, a frequency-dispersive shoulder at a lower temperature (<i>T</i>_s) around 425-450 K, which is associated with polar nanoregions (PNRs), and second, from ferroelectric to paraelectric transition at the Curie temperature (<i>T</i>_c) approximately between 580 and 650 K. The impedance analysis reveals the negative temperature coefficient of resistance behavior of the specimens. The broad and asymmetric relaxation peaks obtained from modulus spectroscopy demonstrate a wide range of relaxations, suggesting non-Debye-type behavior. Furthermore, the conductivity studies provide insights into understanding the transport phenomena in the samples. The oxygen vacancies resulting from the addition of LaCoO₃ into the Na_0.5Bi_0.5TiO₃ ceramics are responsible for the relaxation and conduction processes, and the charge carrier is doubly ionized oxygen ion vacancies. All samples except for LCNBT10 at 1 kHz exhibit a negative magnetodielectric response.