ESR centers in reduced stabilized zirconia

Abstract

Stabilized zirconia, when exposed at high temperature to a reducing atmosphere, becomes colored, and a pronounced room-temperature ESR signal appears. The concentration of the color centers was determined by optical absorption in the uv–visible range, and the concentration of the paramagnetic centers was determined by electron paramagnetic resonance in the X band. We found that the concentrations of the centers causing the two effects have the same P(${\mathrm{O}}_2$ ${)}^{\mathrm{-}1/4}$ dependence on the oxygen pressure, a dependence that agrees with a simple model; however, the ESR signal varies strongly from crystal to crystal. We conclude from these results that both effects are caused by the same center, most probably an impurity with a total concentration of ${10}^{\mathrm{-}3}$ mol, which has captured an electron. From the ESR results the level of this electron state is ≃1.60 eV below the conduction band. The oscillator strength for optical absorption was found to be ${\mathit{f}}_{\mathit{O}}$≃0.01.