Synthesis and physicochemical properties of thallium and lithium tungstate

On the basis of results of X-ray phase and differential thermal analyses phase diagram of the system Tl2WO4-Li2WO4 has been plotted. Formation of compound of the composition 1:1, incongruently melting at 500 deg C, in the system is ascertained. Thallium and thallium-lithium tungstates form eutectics, containing 34 mol.% Li2WO4 and melting at 460 deg C. The thallium-lithium tungstate prepared is characterized by reversible polymorphous transformations at the temperatures 200, 420 and 470 deg C. By X-ray diffraction studies it has been ascertained that TlLiWO4 at room temperature is isostructural to tridymite-like structural type of monoclinic beryllonite