Microwave-assisted synthesis of nanocrystalline MWO4 (M: Ca, Ni) via water-based citrate complex precursor

Abstract Nano-sized MWO 4 (M: Ca, Ni) powders, which have scheelite and wolframite type structure, were successfully synthesized at low temperatures by a modified citrate complex method assisted by microwave irradiation. The citrate complex precursors were heat-treated at temperatures from 300 to 500 °C for 3 h. Crystallization of the CaWO 4 and NiWO 4 nano-sized powders were detected at 300 and 350 °C, respectively, and completed at a temperature of 400 °C. Most of the CaWO 4 and NiWO 4 powders heat-treated between 350 and 450 °C showed primarily spherical and homogeneous morphology. The average crystallite sizes of CaWO 4 and NiWO 4 were between 12 and 35 nm and between 14 and 29 nm, respectively, showing an ordinary tendency to grow with temperature.