Effect of oxygen environment on the decomposition and crystallization of an aqueous sol-gel derived zirconium acetate gel

A precursor gel was prepared by desiccation of an aqueous solution of zirco nium acetate and pyrolyzed to form crystalline powders in selected gas envi ronments. Thermal analysis, X-ray powder diffraction, mass spectrometry and Fourier transform infrared spectroscopy were used to investigate the decom position of the gel and the transformations occurring during pyrolysis to 8 00 degrees C in nitrogen, air and oxygen. Three transition temperatures wer e detected: the amorphous-to-cubic crystal transformation, cubic-to-tetrago nal transformation, and the initiation of tetragonal-to-monoclinic transiti on. The presence of molecular oxygen decreased the crystallization temperat ure, increased the grain size of the tetragonal crystals formed and decreas ed the temperature at which the tetragonal-to-monoclinic transformation was initiated. The decrease in the crystallization temperature in the presence of oxygen occurred despite an increase in the temperature corresponding to the loss of the major portion of the organic component of the gel.