CRYSTAL-STRUCTURE OF THE HIGH-TEMPERATURE PROTONIC CONDUCTOR SRCEO3

The crystal structure of the perovskite-like high-temperature protonic conductor SrCeO3 has been studied with single-crystal and powder X-ra y diffraction. SrCeO3 crystallizes in the orthorhombic space group Pbn m, Z=4, with the unit-cell parameters a = 6.0117(4) angstrom, b = 6.15 38(5) angstrom and c = 8.5886(9) angstrom. The structure was refined t o a weighted R value of 0.0226 for the single-crystal data. The oxygen coordination around cerium is almost perfectly octahedral, whereas th e SrO12 polyhedra are rather distorted. SrCeO3 is isostructural with a nother high-temperature protonic conductor, BaCeO3, but displays an ap preciably higher degree of lattice distortion.