Synthesis and structure of two new bismuth cadmium vanadates, BiCdVO5 and BiCd2VO6, and structures of BiCa2AsO6 and BiMg2PO6

The new compound BiCdVO5 was synthesized and its structure was determined by single crystal X-ray diffraction. This compound crystallizes in the acentric polar space group Pc2(1)n with cell dimensions of a=5.505(2), b=11.699(4), and c=14.276(4) Angstrom. Bi(III) is five-coordinate and its environment is distorted tetragonal pyramidal. These pyramids share edges to form ribbons parallel to the a axis. The two Cd(II) sites exhibit a distorted octahedral environment, and the two V(V) sites show a distorted tetrahedral environment. The new compound BiCd2VO6 was found to be isostructural with BiCa2VO6, and its structure was refined from X-ray powder diffraction data. The structures of BiCa2AsO6 and BiMg2PO6 were refined from neutron powder diffraction data and are compared to those of BiCd2VO6 and BiCa2VO6. All four compounds described have (Bi-O-2)(-) ribbons. (C) 2000 Elsevier Science Ltd. All rights reserved.