Impedance Spectroscopy of (Bi1/2Na1/2)TiO3-BaTiO3 Based High-Temperature Dielectrics

Abstract

The dielectric properties of CaZrO3 (CZ) modified 0.94Bi(1/2)Na(1/2)TiO(3) (BNT)-0.06BaTiO(3) (BT) and 0.82(0.94BNT-0.06BT)-0.18(K1/2Na1/2)NbO3 have been investigated by impedance spectroscopy over a wide temperature range. The presence of a highly polarizable phase in addition to a bulk response is revealed by electric modulus (M) spectra in both systems. The relaxation frequency of the polar phase follows the Vogel-Fulcher law below the Burns temperature which decreases with increasing CZ content. The dc conductivity of the ceramics is dominated by the bulk response which follows the Arrhenius law with an activation energy ranging from 1.4 to 1.7eV and has an oxygen partial pressure dependence consistent with n-type semiconductivity. This information is pertinent to on-going compositional development of relaxor-based high-temperature dielectrics.