Structural and dielectric properties of relaxor Sr_0·5Ba_0·5Bi₂Nb₂O₉ ceramic

Abstract

Sr_0·5Ba_0·5Bi₂Nb₂O₉ ceramic was prepared by a conventional solid state reaction method and studied using X-ray powder diffraction and dielectric measurements. At room temperature, an orthorhombic structure was confirmed and their parameters were obtained using the Rietveld method. Dielectric properties were studied in a broad range of temperatures and frequencies. Typical relaxor behaviour was observed with strong dispersion of the complex relative dielectric permittivity. The temperature of the maximum dielectric constant T _m decreases with increasing frequency, and shifts towards higher temperature side. The activation energy E _a≍0·194±0·003 eV and freezing temperature T _f ≍371±2 K values were found using the Vögel-Fulcher relationship. Conduction process in the material may be due to the hopping of charge carriers at low temperatures and small polarons and/or singly ionised oxygen vacancies at higher temperatures.

Keywords:

• Bismuth layered
• Aurivillius
• Relaxor