CRYSTAL-STRUCTURE OF A METASTABLE FORM OF INDIUM ORTHOVANADATE, INVO4-I

The compound InVO4-I has been obtained with a good purity level from a chimie douce process. Using X-ray powder diffraction data, its crysta l structure has been determined by analogy with isostructural compound s crystallizing with the so-called alpha-Mn-MoO4 type structure. The c rystal symmetry is monoclinic (space group C2/m) and the unit cell par ameters are a = 10.271(1) Angstrom, b = 9.403(1) Angstrom, c = 7.038(1 ) Angstrom, and beta = 105.08(1)degrees. The structure has been refine d by the Rietveld method (R(F) = 0.030 and R(wp) = 0.098 for 360 refle ctions). The structure is based on compact In4O16 groups of four edge- sharing InO6 octahedra linked to each other by VO4 tetrahedra. Each In 4O16 cluster contains two In1O(6) and two other In2O(6) octahedra and the corresponding In1-O and In2-O mean distances are 2.14 and 2.17 Ang strom. The mean value for the V-O bond length is 1.71 Angstrom. Relati onships with the stable indium vanadate and related phases are discuss ed. (C) 1995 Academic Press, Inc.