The first results were presented on heterovalent substitution of alkaline-earth cations Ca2+ for Yb3+ in oxide ion conductor Yb2Ti2O7. (Yb1-xCax)2Ti2O7 (x = 0.05, 0.1) was synthesized using mechanical activation of the oxides Yb2O3, CaO, TiO2 and subsequently sintering at 1400C in air, and their electrical conductivity was measured from 300 to 950C. (Yb0.9Ca0.1)2Ti2O7 synthesized at 1400C from a mechanically activated oxide mixture had the highest conductivity among the pyrochlores studied so far: 2 x 10-2S/cm at 740C, i.e., 0.2S/cm at 1000C. Neutron diffraction data indicate that the Сa2+ in (Yb0.9Ca0.1)2Ti2O7 occupies the Yb site, leading to the formation of O vacancies in the O2 (48f) site and the presence of oxygens in the O3 (8b) site, normally vacant in ordered pyrochlores. No evidence of Ca substitution on the Ti site was found.

Effect of the Ca-Doping on the Electrical Conductivity of Oxide Ion Conductor Yb2Ti2O7. A.V.Shlyakhtina, P.Fedtke, A.Busch, I.V.Kolbanev, T.Barfels, M.Wienecke, A.E.Sokolov, V.A.Ulianov, V.A.Trounov, L.G.Shcherbakova: Solid State Ionics, 2008, 179[21-26], 1004-8