Synthesis and study of compounds of the general formula MITh2(VO4)3 (MI = Li, Na, Ag, K, Rb, Cs, Tl)

Abstract

Double vanadates of thorium and univalent metals with r(MI) < 1.6 A were prepared by high-temperature solid-phase reactions. Representatives of this series with larger MI atoms were prepared by the solgel method. The compounds crystallize in three structural types: zircon for Li and Na derivatives, scheelite for AgTh2(VO4)3, and potassium thorium vanadate for the compounds containing K, Rb, Cs, and Tl. Thus, two morphotropic transitions are observed in the series of the compounds studied. The bands in the IR spectra were assigned, and the effect of the site symmetry of the VO4 tetrahedra on the number of absorption bands was revealed. The incongruent melting points of the compounds were determined by differential scanning calorimetry.