Impedance Spectroscopy of ( Bi _1/2 Na _1/2 ) TiO ₃ – BaTiO ₃ Based High‐Temperature Dielectrics

Abstract

The dielectric properties of CaZrO 3 ( CZ ) modified 0.94 Bi 1/2 Na 1/2 TiO 3 ( BNT )–0.06 BaTiO 3 ( BT ) and 0.82(0.94 BNT –0.06 BT )–0.18( K 1/2 Na 1/2 ) NbO 3 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 1.7 eV 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.