A reinvestigation of the crystal structure of α-Pb2BiVO6

• Published in: Solid state sciences 2004-08, Vol.6 (8), p.783-790
• Main Authors: LABIDI, O, WIGNACOURT, J. P, ROUSSEL, P, DRACHE, M, CONFLANT, P, STEINFINK, H
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Crystalline state (including molecular motions in solids); Exact sciences and technology; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Theory of crystal structure, crystal symmetry; calculations and modeling
• ISSN: 1293-2558; 1873-3085
• DOI: 10.1016/j.solidstatesciences.2004.03.024

A previously reported beta phase for Pb2BiVO6 has been characterized as a stable phase, and the phase transitions alpha - > beta and beta - > delta were identified in the mother phase as well as in Pb2BiV1-xMxO6-y solid solutions (M = Cr, Mn); the high temperature form S-Pb2BiVO6 eventually decomposes at 480 deg C to a mixture of PbBiVO5 and Pb4BiVO8 before showing recombination at 650 deg C. The related substituted compositions behave the same way. The crystal structure of alpha-Pb2BiVO6 (I) is monoclinic, P21/n, a = 7.717(3) A, b = 5.845(3) A, c = 29.081(8) A, beta = 94.27(l)DG, Z = 8. Oxygen atoms are in tetrahedral interstices formed by four Bi and Pb atoms. These tetrahedra articulate by Bi-Pb edge sharing in two dimensions parallel to the b axis to form infinite chains. Mixed O(V Bi Pb)4 tetrahedra bridge the O(Bi Pb)4 ribbons by edge sharing to complete the three-dimensional articulation of the structure. alpha-Pb2BiV1-xMnxO6-y (x = 0.06) (II) is monoclinic, P21/m, a = 7.684(3) A, b = 5.822(3) A, c = 14.708(6) A, beta = 100.92(l)DG, Z = 4. Tetrahedral units of O(2Bi 2Pb) are also present in (II). They form dimers O2Bi4Pb4 by Bi-Bi edge sharing. The dimers form a chain along the b axis by sharing Bi-Pb edges. Two independent MO4 tetrahedra (M = V, Mn) are present in which one has V/Mn mixed occupancy. Both tetrahedra show statistical disorder by rotation around a V-O apex. The disordered tetrahedral oxygen atoms are part of the coordination sphere of Bi and Pb. The matrix {-100, 0-10, 102} relates the structures and unit cells of [I], and [II].