Synthesis and characterization of metal tungstates by novel solid-state metathetic approach

Novel solid state metathetic approach (SSM) (ACl2 + Na2WO4 → AWO4 + 2NaCl, A = Ca, Sr, Ba, Zn, Mn, Ni) assisted by microwave energy has been successfully applied to the synthesis of tungstates of scheelite- and wolframite-type that are of technological importance. Well crystalline phases of scheelite-type tungstates, MWO4 (M = Ca, Sr, Ba) have been synthesized where the characteristics of SSM reaction and the formation of high lattice energy by-product NaCl drives the reaction toward completion. Among wolframite-type tungstates, single-phase ZnWO4 is synthesized by SSM reactions at ambient conditions and MWO4 (M = Ni, Mn) are synthesized after subjecting the amorphous product to moderate temperature of heating (around 500 °C for 6 h). This alternative method of synthesis where the metathesis reactions proceed in solid state has features like: simple method of synthesis, cost-effectiveness, high yield, easy scale up, and thus has advantages over already known methods of synthesis.