A new family of compounds with tetrahedral anions: PbnBiOn(XO4), X = V, P,As, n=1, 2, 4. A comparison with lead oxysulfates PbnPbOn(SO4)

The thermal behavior and crystallographic characteristics of nine compounds , PbnMOn(XO4) with M = Bi, Pb, X = V, P, As, S and n = 1, 2, 4, are reporte d. A previously reported gamma phase for Pb2BiO2(VO4) was shown to consist of a mixture of PbBiO(VO4) and Pb4BiO4(VO4) that resulted from a kineticall y controlled decomposition of Pb2BiO2(VO4) at elevated temperatures. The re lationship between the alpha, beta, and delta transitions for Pb2BiO2(VO4) was clarified. All of these phases contain the tetrahedral anion XO4 that i mparts thermal and structural similarities as well as specifications that c an be ascribed to anion size differences. (C) 2001 Editions scientifiques e t medicales Elsevier SAS. All rights reserved.