Claudia J. Rawn

Sr2Bi2O5: A structure containing only 3-coordinated bismuth

Abstract The bismuth(III) strontium oxide Sr 2 Bi 2 O 5 has been synthesized in the low-temperature form, and studied using both single-crystal X-ray and powder neutron diffractometry. All bismuth atoms are in an unusual threefold coordination with oxygen. The compound crystallizes in the orthorhombic space group Pnma with Z = 4 and X-ray cell parameters a = 14.261(3), b = 6.160(2), c = 7.642(3)A. A superlattice, visible in long exposure precession photographs, exists along c (2 × 3.8A). This is due to the ordering of oxygen and vacancies along the c -axial direction, and to resulting displacements of the Bi atoms along c . The structure consists of an ordered intergrowth, along the a -axial direction, of slabs of inverse NiAs-type, with composition Sr 2 O 4 and strings of Bi O Bi···□···Bi O Bi···, where □ represents an oxygen vacancy.