Comparison study on the high-temperature phase stability of CaO-doped zirconia made using different precipitants

CaO-doped zirconia was synthesized by a traditional sol–gel method using both NaOH and ammonia solutions as precipitants. The high-temperature phase stability was investigated following calcining at 1000 °C for 2 h. XRD and Raman spectra were used to characterize the crystal form of the zirconia. The results indicate that the concentration of OH− introduced into the ZrO2 lattice is the main factor controlling the crystal form of nanosized zirconia using NaOH solution as the precipitant. CaO-doped zirconia synthesized using an ammonia solution as the precipitant can maintain the tetragonal phase after calcining at 1000 °C for 2 h.