STRUCTURE DETERMINATION OF A NEW PEROVSKITE PHASE IN THE BA K BI NA O SYSTEM

During the synthesis by electrodeposition of Ba1-xKxBiO3 superconducting crystals, black crystals of a new phase were grown at the anode. Chemical analysis (WDS) revealed the presence of sodium in these crystals. The chemical formula, Ba3.12K0.66Bi3.37Na0.63O12, and the structure have been determined from single crystal X-ray diffraction. The structure is perovskite-like with a = 8.54Å=2ap, ap being the lattice parameter of the perovskite cell. The doubling is due to a 1(B′):3(B) ordering on the octahedral sites. The B sites are occupied by Bi5+ cations whereas the B′ sites are occupied by a mixture of Na and Bi cations. The latter should be disproportionated into Bi3+ and Bi5+. No sign of diamagnetism has been detected in these crystals at low temperature. © 1991 Academic Press, Inc.