Studies of effects of trivalent impurity ions on the transition to the superionic state of fluorites

Abstract
It is found that the temperature Tc of transition to the superionic state of some fluorites is depressed by doping with trivalent cations, falls of up to approximately 200K being observed for doping concentrations of up to approximately 9 mole per cent. Calculation suggests that complexes formed by the impurity cations and charge-compensating interstitial anions act as traps for thermally-generated anion interstitials, thus reducing the energy of formation of anion Frenkel pairs and also of Tc.