Industrial precipitation of zirconyl chloride: The effect of pH and solution concentration on calcination of zirconia

In situ and ex situ X-ray diffraction, and transmission electron microscopy were used to investigate the calcination of four samples of zirconia manufactured using two different zirconia reactant solution concentrations (0.81 M and 1.62 M) with precipitation carried out at pH 3 and 12. The calcinations were investigated over the temperature range from room temperature to 1000 °C. It was found that varying the precipitation conditions resulted in differing calcination routes; it is believed that variations in particle size and initial degree of hydration are responsible for these differences. It was also found that the initial phase produced after calcination was tetragonal zirconia, which underwent a process of crystallite growth to a size of ∼30 nm before transformation from tetragonal to monoclinic.