Electron spin resonance, electrical and mechanical techniques were used to study yttria-stabilized single crystals. The effect of defects which were produced by reduction at 1800C in vacuum (10-5mm Hg), followed by quenching, was investigated. It was concluded that an increase in the excess electron concentration during heat treatment was evidence of a mixed (ionic/electronic) conductivity. For a given yttria content, the

observed differences in conductivity could be attributed to disordering of the O sub-lattice, due to the differing concentrations of O vacancies and excess electrons. The conductivity of annealed samples was higher than that of non-annealed samples. The activation energies for conduction were equal to 1.199eV for unannealed samples, and equal to 1.186 or 1.194eV for annealed samples.

M.Hartmanova, A.A.Urusovskaya, M.Valko, T.V.Oreshnikova: Solid State Phenomena, 1994, 39-40, 227-30