Changes which occurred in the properties of the tetrahydrate, during dehydration at temperatures of between 295 and 673K, were studied. A relatively low conductivity was measured before dehydration, and this was associated with an activation energy of 38.2kJ/mol. This was attributed to the movement of H+ ions. During dehydration, the nature of the effective charge carrier and of the conduction mechanism changed. Upon heating to about 310K, a sudden increase in the conductivity occurred and it remained high at temperatures of up to 383K. On the other hand, the conductivity of the fully dehydrated samples was very low.

M.V.Susic, D.M.Minic, U.B.Mioc: Solid State Ionics, 1982, 6[2], 139-43