Dielectric, structural and Raman studies on (Na_0.5Bi_0.5TiO₃)_(1-x)(BiCrO₃)_x ceramic

Abstract

Dielectric, structural and Raman investigations were carried out on a perovskite-based solid solution of (NBT)_{(1 - x)}(BiCrO₃)_x (x = 0.00, 0.05, 0.10 and 0.15). The crystal structure is rhombohedral, R3c, for these compositions and the anti-phase (a ^- a ^- a ^- ) tilt angle decreases with increasing BiCrO₃ content. The temperature and frequency dependent dielectric measurements show that the phase transition temperatures T_d and T_{R - T} decrease, while T_m increases, almost linearly with an increase in BiCrO₃ content. An anomalous increase in the relative dielectric permittivity is observed at higher temperature (T > T_d) and higher BiCrO₃ content. However, at lower temperature (T > T_d) the dielectric permittivity decreases with an increase in BiCrO₃ content. These effects are explained on the basis of the dynamics of oxygen defects produced due to charge compensation. The defect related bands are observed in the Raman spectra of (NBT)_{(1 - x)}(BiCrO₃)_x.