The properties of pressed pellet samples were determined at temperatures of between 330 and 560K. A sudden increase in the conductivity, and a change in the slope of the Arrhenius plot, were found at 435K. These were attributed to a transition from a normal to a superionic phase. The migration enthalpies were found to be equal to 0.44 and 0.34eV for the normal and superionic phases, respectively.

B.K.Verma, O.P.Srivastava, H.B.Lal: Physica Status Solidi B, 1981, 64[2], 467-73