The layer crystal structure of [In2(C2O4)3(H2O)3]•7H2O and microstructure of nanocrystalline In2O3 obtained from thermal decomposition

A new indium oxalate, [In-2(C2O4)(3)(H2O)(3)].7H(2)O, with a layered structure has been synthesised from precipitation methods at room temperature. It crystallises with a monoclinic symmetry, space group P2(1)/c (No. 14), a = 8.7456(1) Angstrom, b = 11.1479(2) Angstrom, c = 21.9376(4) Angstrom, beta = 112.1(1)degrees, V = 1979.98(6) Angstrom(3) and Z = 4. The structure is built from neutral [In-2(C2O4)(3)(H2O)(3)] corrugated layers, between which water molecules are intercalated. The layers are built from chains with two different sequences of indium atoms and bichelating oxalate groups. Two independent indium atoms are present in the structure with two coordination polyhedra, i.e., InO8 as a distorted square-based antiprism and InO7 as a nearly regular pentagonal-based bipyramid. The thermal decomposition has been studied in situ by temperature dependent X-ray diffraction and thermogravimety. The final product is nanocrystalline indium oxide. The microstructure of the oxide has been characterised with both the Voigt/Langford method based on the integral breadth and the whole pattern fitting approach. The size of the isotropic crystallites increases from 322 to 924 Angstrom, while microstrains decrease, in the annealing temperature range 500-750 degreesC. (C) 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved.