Synthesis, structure determination from powder diffraction data and thermal behaviour of titanium(IV) oxalate [Ti 2O 3(H 2O) 2](C 2O 4)·H 2O

Abstract

A titanium(IV) oxalate, [Ti 2O 3(H 2O) 2](C 2O 4)·H 2O, has been synthesised in a polycrystalline form in the course of the study of precursors of PZT type oxides. Its crystal structure has been solved ab initio from powder diffraction data collected with conventional monochromatic X-rays. The symmetry is orthorhombic, space group Cmca, with cell dimensions a=15.494(2) Å, b=10.491(1) Å, c=9.700(1) Å and Z=8. The structure consists of inorganic corrugated layers of corner-sharing TiO 6 octahedra, which form infinite TiOTi connections, linked together by the oxalate anions. The titanium environment is discussed with regard to bond-valence calculations. The thermal behaviour of this compound has been studied by temperature-dependent X-ray diffraction and thermal analyses. In the course of the dehydration process, the partially dehydrated phase [Ti 2O 3(H 2O) 2](C 2O 4) has been isolated and its structure has been solved from in situ X-ray powder diffraction data. Its crystal structure determination has shown that the framework of the precursor is preserved. The complete decomposition scheme into anatase is also described.