E.s.r. study of occurrence of Ni3+ ions in MgO—NiO—Li2O solid solutions

Abstract

The occurrence and the stability of the e.s.r. signal at g= 2.1693 attributed to Ni³⁺ ions in MgO have been investigated. The intensity of the signal, present only in MgO—NiO—Li₂O specimens, can be partially reduced upon outgassing at temperatures in the range 250–500°C. Oxidation in air at the same temperature as evacuation restores it, but the restored signal does not decrease on a subsequent vacuum treatment.

This behaviour has been discussed in terms of the oxygen adsorption processes and of the topological distribution of Ni³⁺ ions. The results point to the presence of different forms of oxygen adsorbed on the surface.