THE THERMAL STUDY OF VANADYL TARTRATES OF FORMULAS M(X)(VO)Y(L)2.NH2O(WHERE M IS NA, SR, CA AND BA L IS TARTRATE), PRECURSORS OF MIXED OXIDES

The thermal decomposition of some vanadyl tartrates of formulae Na4[(V O)2(C4H2O6)2] . 12H2O, Ca(VO)(C4H4O6)2 . 6H2O, Sr(VO)(C4H4O6)2 . 5H2O and [Ba2(VO)2 (C4H2O6)2(H2O)8] have been studied by TG and DSC techniq ues under non-isothermal experimental conditions. All the compounds pr esent a three-step decomposition pattern (dehydration, ligand pyrolysi s and evolution of the inorganic residue), leading to a residue corres ponding to several vanadates and oxides. Kinetic analyses of the dehyd ration curves have been performed using the Satava integral method: ra ndom nucleation, order of reaction 1.5 and the Johnson equation have g iven the best correlation factors. In order to obtain mixed oxides, th e complexes were fired in three different atmospheres. The oxides obta ined from alkaline-earth vanadyl tartrates depend on the atmosphere em ployed.