Non-stoichiometry, electrical properties, and cation diffusion in highly non-stoichiometric Co 1− xO—I. Experimental†

Abstract

Non-stoichiometry and mass and electrical transport properties were measured in pure, single crystal Co 1− x O with 0.003 ⩽ x ⩽ 0.044. Electrical conductivity and thermopower were measured at temperatures from 1000°C to 1200°C in a range of oxygen partial pressures, P o 2 , of 0.21 to 32atm. The cation tracer diffusion coefficient was measured at 1200°C in the same pressure range, and at 3.7 atm from 1064°C to 1200°C. Electrical properties were used to locate the Co 1− x O/Co 3O 4 phase boundary. All properties show a stronger p o 2 , dependence than predicted by a point defect theory based on ideal solutions. Analysis of the temperature dependence of hole mobility produced an activation energy for small polaron hopping of 0.37 ± 0.04 eV.