Alternating-current conductivity measurements were carried out at 0.5 to 20kHz. The results, for temperatures of between 20 and 140C, could be described by the expression:

σT (SK/cm) = 8300 exp[-0.134(eV)/kT]

From these, and other results, it was deduced that the Haven ratio at temperatures of between 100 and 140C was equal to 0.9.

J.G.Vlasov, J.E.Ermolenko, S.V.Glazunov, V.V.Kolodnikov: Solid State Ionics, 1989, 34[3], 157-60