In Situ Study of the High-Temperature Solid-Phase Synthesis of Zinc Tungstate in the Zinc Oxide–Tungsten Oxide System

Zinc tungstate is an inorganic luminescent material with the self-activation of luminescence when exposed to ultraviolet (UV) radiation, X-rays, and cathode rays. There are two ways to synthesize this compound: the liquid-phase sol-gel method and solid-phase high-temperature synthesis in an oxygen-containing environment. Phase transformations are studied during the solid-phase high-temperature synthesis of ZnWO4 from a mixture of micron-sized powders of ZnO and WO3 oxides upon heating to 900°C and storage for 30 min in air. It is experimentally established that during high-temperature solid-phase synthesis, in the entire studied temperature range, zinc oxide does not change its crystalline structure upon heating, while tungsten oxide undergoes a series of transformations from the monoclinic phase to the orthorhombic phase. The formation of the crystalline hexagonal phase of zinc tungstate begins in the temperature range from 700 to 750°C. At a maximum temperature of 900°C, the phases ZnWO4 (monoclinic), ZnO (hexagonal), and WO3 (orthorhombic) coexist simultaneously; further storage at this temperature leads to an increase in the content of the zinc-tungstate phase and a decrease in the concentration of other phases.