Fabrication and Characterization of W-Substituted ZnFe2O4 for Gas Sensing Applications

A sol–gel technique was successfully employed in creating pure and W-substituted zinc ferrite, with nominal compositions of ZnFe2−2xWxO4 (0.0 ≤ x ≤ 0.15). For the purposes of investigating the physical and chemical properties of the generated powders, several analytical techniques were used. In TEM images of all the compositions, mixed-shaped particles (cubic, spherical, and hexagonal) were observed. The crystallite size decreases from 82 nm (x = 0.0) to 32 nm (x = 0.15) with an increase in the W doping contents in the ZnFe2O4 lattice. The microstrain increases with increasing W doping content. Furthermore, the surface area of pure ZnFe2O4, 0.05 W-ZnFe2O4, 0.10 W-ZnFe2O4, and 0.15 W-ZnFe2O4 NPs were calculated as being 121.5, 129.1, 134.4 and 143.2 m2 g−1, respectively, with a mesoporous pore structure for all ferrite samples. The calculated BJH pore size distribution was within the range of 160 to 205 Å. All W-doped ZnFe2O4 samples show H-M loops with paramagnetic characteristics. The magnetization (M) directly increases by increasing the applied field (H) without achieving saturation up to 20 kA/m. For comparison, the magnetization at 20 kA/m gradually decreases with increasing W doping content. Among all the synthesized samples, the 0.15 W-ZnFe2O4 NPs demonstrated the highest sensitivity towards acetone gas at 350 °C.