Defect Structure of Indium Oxide

I. Dependence of Oxygen Partial Pressure and Temperature on the Electrical Conductivity and Thermoelectric Power of High Purity Sintered Indium Oxide

Abstract

The electrical conductivity (ac and dc) and the thermoelectric power of high purity polycrystalline indium oxide prepared from 6-nine indium metal were measured as a function of temperature 300°-600°C and oxygen partial pressure 1.5-760 mmHg (Po₂+P_argon: 760 mmHg) under the homogeneous nonstoichiometric phase. The results of thermoelectric power measurements indicated an n-type semiconductor in all these experimental conditions. The ac conductivity was nearly independent on frequency over the range 1-80 KHz from 300°-600°C. The electrical conductivity was well represented by the relation σ ?? PO₂^-1/4 in nearly intrinsic range at above ca 400°C, and the thermoelectric power had also roughly same -1/4 pressure dependence. Therefore, the predominant defects in oxygen deficient region were presumed any one: a) singly ionized oxygen vacancies, b) doubly ionized indium interstitials, c) coexistence of both a) and b). In spite of using the high purity specimen at lower temperature range, impurity conduction was observed. Thereby, it must be inferred that purity of indium oxide requires at least concentration of impurity below 10¹⁴ atom/cm³, so as to obtain exact intrinsic character at lower temperature range.