Electrical Conduction in Reduced Single Crystals of Barium Titanate

Abstract

Temperature dependence of electrical conductivity and Hall effect of the barium-titanate crystals reduced by hydrogen were studied at temperatures -195∼165°C. The hydrogen reduction was carried out at above 800°C. The optical absorption in the reduced crystals was observed. Electron spin resonance absorption due to oxygen vacancy with a captured electron was observed in the slightly reduced crystals. Thermal activation energies obtained from temperature dependence of electrical conductivity showed different values in each phase of BaTiO₃ crystal. Carrier concentration calculated from Hall coefficient is 10¹⁷∼10¹⁹/cc and Hall mobility ranges from 10^-2 to 1 cm² v^-1·s^-1 at room temperature. A hydrogen-atom-like model is proposed for the captured electron in oxygen vacancy in the reduced barium-titanate crystals. The electrical conduction seems to be reasonably explained by a band model theory.