High Frequency Conductivity of NiO

Abstract

The conductivities of 1.2, 7.9 and 12.6 ppm (weight ratio) Li-substituted NiO are measured at high frequencies up to 24 GHz in the temperature range 110° to 450°K. The conductivity at high frequencies can be expressed as the sum of a temperature-dependent conductivity σ₁ and a temperature-independent additive conductivity σ₂. The former σ₁ is independent of frequency until microwave region but the latter σ₂ is strongly dependent on freqnency. The frequency dependence of σ₂ can be represented by the dispersion formula for the dielectric loss due to the hopping of charge carriers around imperfections. The staying time at a lattice site is determined: τ=2.2×10⁻¹⁰ sec. A lack of temperature dependence of σ₂ implies that the staying time τ does not depend on temperature and further that the holes are not selftrapped. The conduction mechanism in NiO is rather illustrated as something analogous to impurity conduction.