Electrical conductivity and thermogravimetric studies of single crystalline cobaltous oxide

Abstract

Electrical conductivity and thermogravimetric measurements on single crystalline cobaltous oxide indicate that the electronic and atomic defect concentration is a function of the 1 4 power of the oxygen partial pressure over the temperature range of 900°–1200°C and oxygen partial pressure of 10°−10 −4atm. These results are in agreement with singly ionized cation vacancies as the predominant defect. The enthalpy of defect formation, Δ H f 0, was obtained from data of conductivity, of vacancy concentration and also determinations of constant weight for the same defect concentration. The results were 13·2, 13·8 and 13·4 kcal/mole, respectively. Activities of oxygen and cobalt in CoO relative to CoO 1.002 have been determined as well as the entropies of activation for electrical conduction and formation of nonstoichiometric disorder. Measurements of the electrical conductivity while at thermodynamie equilibrium at constant composition confirm that it is possible to quench in a constant concentration of disorder. Mobilities for electron holes at fixed compositions for these data were also determined.