Pb2BiO2PO4, a New Oxyphosphate

✍ Scribed by Ariane Mizrahi; Jean-Pierre Wignacourt; Hugo Steinfink

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 285 KB
• Volume: 133
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1997.7520

✦ Synopsis

Pb 2 BiO 2 PO 4 is orthorhombic with space group Pnma, a ‫؍‬ 5.930(4), b ‫؍‬ 9.079(10), c ‫؍‬ 11.473 (6) A s at room temperature, Z ‫؍‬ 4, and a congruent melting point of 860°°C. The structure was solved from single crystal and powder diffraction data. The PO 4 ion can occupy two energetically equivalent positions causing two oxygen atoms to be disordered. The structure can be described on the basis of several motifs. Infinite chains of BiO 2 rectangular pyramids formed by edge-sharing parallel to the a axis that are linked by lead atoms and phosphate anions. Bi can also be considered as present in a trigonal prismatic environment of oxygen atoms in which one corner of a triangular face is unoccupied. Presumably the 6s 2 lone pair extends toward that apex. Pb is bonded to six oxygen atoms forming a distorted octahedron when distances less than 3 A s are considered. When two additional oxygen ions at 3.20(9) and 3.24(5) A s are considered part of the coordination polyhedron it can be described as a bisdisphenoid. This structure is related to structures found in many M II 2 BiXO 6 phases. The Raman spectrum shows the expected frequencies for PO 4 . In addition frequencies are observed that can be assigned to P-O-Bi and P-O-Pb linkages. Intense bands at 143 and 150 cm\ 1 are attributed to internal vibrational modes of the BiO 4 pyramid.