Temperature-dependent Raman spectroscopic study of ferroelastic K₂Sr(MoO₄)

Raman scattering measurements of K₂Sr(MoO₄)₂ were performed in the temperature range of 25-750℃. The Raman spectrum of the low-temperature phase α-K₂Sr(MoO₄)₂ that was obtained by first-principle calculations indicated that the Raman bands in the wavenumber region of 250-500 cm^-1 are related to Mo-O bending vibrations in MoO₄ tetrahedra, while the Raman bands in the wavenumber region of 650-950 cm^-1 are attributed to stretching vibrations of Mo-O bonds. The temperature-dependent Raman spectra reveal that K₂Sr(MoO₄)₂ exhibits two sets of modifications in the Raman spectra at~150℃ and~475℃, attributed to structural phase transitions. The large change of the Raman spectra in the temperature range of 150℃ to 475℃ suggests structural instability of the medium-temperature phase β-K₂Sr(MoO₄)₂.