High-temperature defect structure and electrical conduction in undoped and Li- or Al-doped NiO.

Abstract

Electrical conductivity and thermoelectric power were measured on undoped and Li- or Al-doped NiO at 800°-1400°C. The electrical conductivity (σ) of Li-doped NiO was independent of both oxygen partial pressure (PO2) and temperature at low PO2, which yielded the calculated hole mobility of 0.43cm2/V·s. From the temperature dependence of σ at PO2=105Pa for Al-doped NiO and the hole mobility of Li-doped NiO, the deviation from stoichiometry δ in Ni1-δO was obtained: δ=7.75×10-2exp(-16200/RT). The electrical conductivity for both undoped and Al-doped NiO varied with PO21/4 at a constant temperature, thus leading to the conclusion that doubly ionized nickel vacancies were dominant at high temperatures. The temperature dependence of Seebeck coefficient was inexplicable by means of a thermally activated hopping mechanism indicative of rather wide band conduction of electron holes.