The mixed alkali effect in zinc-compensated (K,Na)-β-gallate

The "mixed alkali effect" was investigated in a Zn-doped K-β-gallate fast ion conductor with partial replacement of the K by Na. A minimum in conductivity occurs at about 0.8 atom fraction Na. A model is proposed in which the site occupancies are determined by the interstitial pair concept, and the conductivity minimum occurs when Beevers-Ross sites are occupied by K+ only. A knee in the Arrhenius plots of samples containing potassium is explained as the onset of activation of K+ away from interstitial complexes bound coulombically to the zinc charge-compensating centers. © 1982.