Hole-ion Mixed Conduction of Orientation-Controlled BaPrO sub( 3- delta ) Thin Film with Mixed Valence States

An in-plane-oriented BaPrO... thin film with mixed valence states has been prepared on an Al...O...(0001) substrate by RF magnetron sputtering. With increasing crystallization temperature (T...), the lattice constant decreases and the orientation changes from the a-axis to the b-axis. The thin film prepared above T... = 800 ...C exhibits a higher proton conductivity than bulk ceramics. The conductivity below 400 ...C decreases with oxygen gas partial pressure, indicating the existence of hole-ion mixed conduction. The valence band consists of O 2p states hybridized with the Pr... (4f...) and Pr... (4f...L) states, which are closely related to the mixed conduction. The energy difference between the top of the valence band and the Fermi level corresponds to the activation energy of holes for the total conductivity below 400 ...C. (ProQuest: ... denotes formulae/symbols omitted.)