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The temperature and frequency dependent dielectric and conductivity properties were measured on as-sintered as well as oxygen annealed KNbO3 ceramics. The results show that in addition to phase transition peaks, well defined relaxation peaks are observed in the temperature range 450–700 K. These peaks could be suppressed by annealing the samples in the oxygen atmosphere. The dc conductivity and maximum dielectric constant values decreases after oxygen annealing. Activation energy, calculated from dielectric relaxation and conductivity data on the samples, suggests that both the processes are due to doubly charged oxygen vacancies formed during sintering process. Dielectric relaxation is attributed to the hopping of oxygen vacancies in the six equivalent sites in perovskite structure. The dielectric and conductivity behaviors are influenced by the density of the samples. The results are explained on the basis of defect concentration and their dynamics.

Electro-caloric effect in lead-free (Ba1−xCax)(Zr0.05Ti0.95)O3 ferroelectric ceramics has been studied for x = 0.05, 0.08, and 0.10. The electro-caloric coefficient as high as 0.253 K mm/kV has been obtained near tetragonal-to-cubic phase transition for x = 0.08. This value is nearly the same as observed in lead-based ferroelectric materials. The higher value of electro-caloric coefficient at x = 0.08 is attributed to the higher polarization flexibility.

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Dielectric, structural and Raman investigations were carried out on a perovskite-based solid solution of (NBT)((1 - x))(BiCrO(3))(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 BiCrO(3) 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 BiCrO(3) content. An anomalous increase in the relative dielectric permittivity is observed at higher temperature (T > T(d)) and higher BiCrO(3) content. However, at lower temperature (T < T(d)) the dielectric permittivity decreases with an increase in BiCrO(3) 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))(BiCrO(3))(x).