Thermal decomposition of titanyl oxalates IV. Strontium and calcium titanyl oxalates

Thermal decomposition of strontium titanyl oxalate tetrahydrate and calcium titanyl oxalate hexahydrate have been studied employing TG, DTA, gas and chemical analysis. The decompositions proceed through three major steps: dehydration, decomposition of the oxalate to a carbonate and the decomposition of the carbonate to yield the final products, the metatitanates. The intermediates of the oxalate decomposition are found to be Sr₂Ti₂O_4+x(CO₃)₂-x(CO₂)_x and Ca₂Ti₂O₄(CO₃)₂, respectively. The entrapment of carbon dioxide in the former and the presence of non-equivalent carbonate groups in the latter are substantiated by their i.r. spectra. The penultimate solid residues are poorly crystalline Sr₂Ti₂O₅CO₃ and amorphous Ca₂Ti₂O₅CO₃. Decompositions of these carbonates are accompanied by growth in particle size of the products, SrTiO₃ and CaTiO₃, respectively.