Semiconductive Single Crystal of BaTiO₃ Reduced in Hydrogen Atmosphere

Abstract

The electrical resistivity, optical transmission, effects of chemical etching, Hall effect, thermoelectric force and electron spin resonance have been studied on single crystals of BaTiO₃ reduced for five hours at temperatures from 400 to 1000°C in a hydrogen atmosphere. The reduction treatment causes a lowering of the resistivity, and enhancement of the infrared absorption centered at 2.3μ and a visible absorption near the optical absorption edge. The single crystals are not always reduced homogeneously. The resistivity of a homogeneously reduced crystal changes abruptly at the three transition temperatures. The sign of the Hall coefficient and the thermoelectric power indicates that the charge carriers in the reduced crystals are electrons. On the basis of the results obtained, a tentative model is proposed for defects in the reduced single crystal.