Density-functional calculations were used to study protonic defects in stoichiometric and substituted La2Zr2O7 pyrochlore oxide. The preferred proton sites were pinpointed in the stoichiometric material and their relative stability determined. Based on these results a continuous migration pathway that enables long-range transport was proposed. In addition, the interaction energies between protons and divalent Ba, Sr, Ca, and Mg dopants located on the La- and Zr-sites were calculated. All interactions were found to be attractive; they were strong in the case of Ba and Mg and quite weak for Sr and Ca suggesting that samples acceptor doped with the latter 2 ions should show the highest proton conductivity.

Protonic Defects in Pure and Doped La2Zr2O7 Pyrochlore Oxide. M.E.Björketun, C.S.Knee, B.J.Nyman, G.Wahnström: Solid State Ionics, 2008, 178[31-32], 1642-7