Effect of calcination temperatures on optical and magnetic properties of FeWO₄ nanoparticles

Calcination temperature is a crucial parameter that can be easily controlled to induce a change in material properties. Herein, iron tungstate (FeWO₄) was synthesized via a hydrothermal method using iron(II) sulfate heptahydrate and sodium tungstate dihydrate as precursors and calcined at the temperature between 300 ^oC and 700 ^oC. With increasing calcination temperature, the saturation magnetization of FeWO₄ nanoparticles decreased from 6.6 emu/g for FeWO₄ to 0.4 emu/g for FeWO4_700, whereas their band gaps increased from 1.95 eV for FeWO₄ to 2.20 eV for FeWO4_700. More crystallinity and crystal defects, and morphological changes at higher calcination temperatures contributed to varying magneto-optical properties of FeWO₄ nanoparticles.