High-pressure Raman study of the Sr₂CaWO₆ double perovskite

Abstract

An in situ Raman spectroscopic study was conducted to explore the pressure-induced phase transformation of Sr2CaWO6 to pressures of 50.8 GPa and room temperature. Group theory yields 24 Raman active modes for Sr2CaWO6, of which 17 are observed at ambient conditions. Upon elevation of pressure to 3.2 GPa, the results suggest some structural changes, possibly a phase transition. At 10.4 GPa, new modes at high frequencies (824 and 903 cm−1) come into existence. As the material is compressed further, the intensities of the bands, especially the W–O stretching modes, observed at 824 and 903 cm−1 become stronger, while those centred at 863 and 937 cm−1 (at 10.4 GPa) decrease significantly, until disappearance. These changes in the spectrum indicate clearly that Sr2CaWO6 undergoes a phase transition at 9.7 ± 0.7 GPa. Upon release of pressure to ambient conditions, a new phase is observed with ten bands compared to the 17 observed in the original phase.