Temperature-dependent Raman scattering study of K2MoO4

This research reports a temperature-dependent Raman scattering study of dipotassium molybdate (K2MoO4) in the 18–913 K temperature range. This study indicates that K2MoO4 crystal exhibits a temperature-induced first-order phase transition at around 578 K from monoclinic phase to incommensurate phase. The phase transition is connected with tilting and/or rotations of the MoO4 tetrahedra that lead to a disorder in the MoO4 sites. An orthorhombic phase (α′-phase) of K2MoO4 was obtained when the low-temperature monoclinic structure was heated or when high-temperature hexagonal structure was cooled. A lattice dynamic calculation was performed by using the classical rigid ion model, in order to predict both wavenumbers and atomic displacements (eigenvectors) for the vibrational modes of the monoclinic phase of K2MoO4 and K2WO4.