It was noted that the protonic conduction of these perovskites arose from the partial replacement of Ce by lower-valence cations. Here, a study was made of compounds with the general formula, R2SrO4, where R was Y, Ho, Tm, Yb, Er or Lu (figure 4). The transport number for protons was shown to attain unity in a reducing atmosphere at 800C. In air, the greatest protonic conductivity was exhibited by Y1.96Ca0.04SrO4. In the case of a reducing atmosphere, the greatest protonic conductivity was exhibited by SrHo1.96Ca0.04O4. Preference was given to the doped compounds because of their chemical stability.

V.B.Balakireva, V.P.Gorelov, O.A.Nevolina: Neorganicheskie Materialy, 1994, 30[2], 234-6 (Inorganic Materials, 1994, 30[2], 224-6)