Investigation of diphasic region in the Pr 2O 3 + Sm 2O 3 mixed oxide system at various temperatures

Abstract

X-ray diffraction studies on mixed rare-earth oxides Pr 2O 3 and Sm 2O 3 quenched at various temperatures were carried out and their phase relationship was analyzed. Mixtures of Pr 2O 3 and Sm 2O 3 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 Pr 2O 3 and Sm 2O 3 exhibit C-type cubic phase at NTP. While Pr 2O 3 retains its cubic phase up to 1200 °C, the Sm 2O 3 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 Sm 2O 3 in Pr 2O 3, 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 Sm 2O 3 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.