Investigation of diphasic region in the Pr2O3Â +Â Sm2O3 mixed oxide system at various temperatures

X-ray diffraction studies on mixed rare-earth oxides Pr2O3 and Sm2O3 quenched at various temperatures were carried out and their phase relationship was analyzed. Mixtures of Pr2O3 and Sm2O3 at different compositions were heated at various temperatures in the range 500-1200 °C and then air quenched. The structures of these quenched samples were analyzed using X-ray diffraction and Raman spectroscopy. Pure Pr2O3 and Sm2O3 exhibit C-type cubic phase at NTP. While Pr2O3 retains its cubic phase up to 1200 °C, the Sm2O3 transformed to B-type monoclinic phase above 800 °C. However, their mixtures when heated at different temperatures showed interesting structural behaviour. For the mixture up to 40 wt.% of Sm2O3 in Pr2O3, no significant change was observed at lower temperatures (∼800 °C), and the C-type cubic phase was observed. As the ratio was gradually increased above 40%, a diphasic region in the range 50-70% was observed, with a combination of both C-type cubic and B-type monoclinic phases. When the temperature was raised to 1200 °C, the 80% of Sm2O3 shows a complete structural transition from cubic to monoclinic phase. Based on the analysis of our results various crystal structures and stability regimes of mixed oxide have been reported.