pH-metric and Raman investigations of zirconium aqueous solutions and gels submitted to a reflux

Abstract Molar solutions of zirconyl chloride corresponding to different steps of neutralization were submitted to reflux at 105°C and Raman spectroscopy and potentiometry measurements were made. The structure of the final products is found to be strongly dependent on the time of reflux as well as on the initial step of hydrolysis. When dried at 50°C, the samples obtained by reflux give amorphous powders whose Raman spectra, differential thermal analysis and powder X-ray diffractograms are described. The nature of the crystallized ZrO 2 (monoclinic or tetragonal) produced by annealing at 470°C is linked to the structure of the amorphous gel. A domain of pH of the initial solution inside which monoclinic zirconia crystallizes directly from the gel is identified.