Although the morphology of the synthesized CaZrO3 grains was similar to that of the as-received ZrO2, their size was greater (Fig. 4). As the density of CaZrO3 (4.68 g/cm3) is lower than that (5.68 g/cm3) of ZrO2,25 a 20% increase in the grain sizes should result compared with the original ZrO2 size. However, such an increase still cannot explain the doubling of grain size shown in Fig. 4, which may arise from grain growth of CaZrO3 assisted by the liquid salt medium.