Local electronic states around H and acceptor ions in SrZrO3 were simulated by using the DV-Xα molecular orbital method to examine their effect upon protonic conductivity. The calculated ioncities of the acceptor dopant ion, M, and the surrounding six O ions, Oi (i = 1 to 6) were found to change with M in the doped oxide, where M was Yb, Y, In, Al or Ga. There was a clear tendency for the protonic conductivity to decrease as the ionicities around the dopant ion, M, deviated further from those around the Zr ion in un-doped oxide. From a geometrical viewpoint, the bond order between M and Oi (i = 1 to 6) ions was another indication for controlling the protonic conductivity. The presence of the slightly weaker M-Oi bond, rather than the Zr-O bond, caused a small expansion of the MO6 octahedron and created a nearly symmetrical space for the proton to move readily to neighboring O sites. These results were also found for BaZrO3 and CaZrO3. Both the ionicity and the bond order were useful parameters for the design of perovskite-type oxides having high protonic conductivity.

Local Electronic Structure and Protonic Conductivity in Perovskite-Type Oxide, SrZrO3. M.Yoshino, K.Kato, E.Mutiara, H.Yukawa, M.Morinaga: Materials Transactions, 2005, 46[6], 1131-9