According to the phase diagram of the ZrO2–CaO system,10 a metastable cubic solid solution region exists
below the eutectoid point at 1140 C and 17% molar CaO composition. In order to study the effect of doping
with Pr2O3, three compositions have been chosen: a molar ratio in ZrO2–CaO on the ZrO2-rich side of the
above mentioned region (composition 1), within the region (composition 2) and on the CaO-rich side of the
region (composition 3).