A review was presented of the structural properties, thermal expansion, electrical conductivity, thermodynamic stability, and surface properties of the pure oxide and of its solid solutions which had face-centered cubic, rhombohedral, tetragonal or layered structures. It was recalled that compounds which were based upon this oxide were much better solid electrolytes than was stabilized zirconia. Unfortunately, they were unstable with regard to reduction at low O partial pressures.

P.Shuk, H.D.Wiemhöfer, U.Guth, W.Göpel, M.Greenblatt: Solid State Ionics, 1996, 89[3-4], 179-96