Influence of thermal treatment on the fo

The paper presents some results concerning the preparation of zirconia powders starting from ZrOCl4·8H2O by using two synthesis methods: (a) precipitation with NH4+, at 90 °C, and (b) thermal decomposition of carboxylate precursors, obtained in the reaction of zirconium nitrate and two different alcohols, 1,3-propanediol (PD) and poly(vinyl) alcohol (PVA), at 150 °C. The precursors obtained at different temperatures have been analyzed by thermal analysis (TG, DTA) and FT-IR spectroscopy. DTA analysis evidenced very clearly that the transition temperatures between zirconia crystalline phases. The prepared powders have been characterized by means of X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). In the case of precipitation method, the presence of the tetragonal phase was observed at 400 °C, while the monoclinic phase appeared at temperatures higher than 400 °C, becoming the major crystalline phase starting with 700 °C. In case of powders prepared by thermal decomposition of carboxylate precursors, the tetragonal phase was formed at temperatures below 700 °C, when the monoclinic phase began to crystallize as a secondary phase. The crystallite size and phase composition were calculated from XRD data for each annealing temperature.