Measurements were made of the electrical conductivity of pure and Sr-doped (0.005 to 1.5mol%) single crystals. At temperatures below 400K, the Arrhenius plot exhibited 2 regions in the case of pure material. The lower-temperature region was attributed to the presence of so-called frozen defects. In the case of Sr-doped crystals, an additional straight-line section appeared in the Arrhenius plot; with a slope that indicated an activation energy of 0.61eV for the migration of cation vacancies.

K.S.Cholokov, V.A.Grishukov: Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, 1970, 13[8], 158-60