Impurity diffusion of Ni in Co 1− xO single crystals

Abstract

Nickel diffusion coefficients have been measured in cobalt oxide Co 1− x O, under oxygen partial pressures of 0.21 atm and 1.5×10 −5 atm in a large temperature range (1000–1600°C). NiO has been deposited as a thin film on the surface of CoO single crystals by rf sputtering. Concentration-penetration curves have been obtained by electron beam microanalysis and by secondary ion mass spectrometry. The results can be described by the relations: D CoO Ni (cm 2/s) = 2.78×10 −2 exp (-2.02 eV/ kT), P O 2 =0.21 atm; and Du CoO Ni (cm 2/s)=1.22×10 −2 exp (-2.15 eV/ kT), P O 2 =1.5×10 −5 atm. We discuss these results and particularly the dependence on oxygen partial pressure. The P O 2 exponent is smaller for impurity diffusion than for self-diffusion. This has been interpreted as evidence for an interaction between Ni atoms and doubly charged vacancies.