Temperature-dependent Raman spectroscopic study of ferroelastic K ₂ Sr(MoO ₄ )

Abstract

Raman scattering measurements of K 2 Sr(MoO 4 ) 2 were performed in the temperature range of 25-750 • C. The Raman spectrum of the low-temperature phase α-K 2 Sr(MoO 4 ) 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 MoO 4 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 K 2 Sr(MoO 4 ) 2 exhibits two sets of modifications in the Raman spectra at ∼ 150 • C and ∼ 475 • C, attributed to structural phase transitions. The large change of the Raman spectra in the temperature range of 150 • C to 475 • C suggests structural instability of the medium-temperature phase β -K 2 Sr(MoO 4 ) 2 .