An IR and Raman study of trigonal triple molybdates M 5 I M 0.5 II Hf1.5(MoO4)6 (MI = K, Tl; MII = Ca, Sr, Ba, Pb)

Abstract

The vibration spectra of triple molybdates M 5 I M 0.5 II Hf1.5(MoO4)6 (MI = K, Tl; MII = Ca, Sr, Ba, Pb) were examined. The internal vibration frequencies of molybdate groups were assigned. The double-charged cations affect the symmetric stretching (v1), bending, and translation vibration frequencies in the Raman spectra. In the IR spectra, the triply degenerate stretching vibration of the MoO4 group (∼890–720 cm−1) is split, and the splitting increases with an increase in the radius of the double-charged cation.