WO3/ZnWO4 microcomposites with potential application in photocatalysis

The paper presents the results of a comprehensive study of the structural, optical and strength features, changes in the morphology of grains of (1-x)WO₃ – xZnO ceramics depending on the concentration of the initial components when they vary. Using the X-ray diffraction method, it was found that mechanochemical grinding of samples of (1-x)WO₃ – xZnO ceramics, regardless of the concentration of the components, does not lead to the initiation of phase transformation processes associated with the formation of the monoclinic ZnWO₄ phase, the formation of which is observed during thermal annealing of samples at a temperature of 1000 °C. Based on data obtained using scanning electron microscopy and X-ray diffraction methods, the dynamics of phase transformations in ceramics of the type WO₃/ZnWO₄ → ZnWO₄ → ZnO/ZnWO₄ was established. It was found that with a given ratio of WO₃: ZnO components equal to 0.7 : 0.3, under selected conditions of mechanochemical grinding and an annealing temperature of 1000 °C, highly ordered single-phase ZnWO₄ ceramics with a wolframite structure can be obtained. Analysis of the optical characteristics and changes in the band gap depending on the ratio of the components showed a direct dependence of changes in the band gap on the phase composition of the ceramics. An assessment of the strength characteristics made it possible to establish that the formation of two-phase WO₃/ZnWO₄ ceramics leads to strengthening of the surface layer, while for two-phase ZnO/ZnWO₄ ceramics a decrease in hardness is observed, the decrease of which directly correlates with changes in the content of the ZnO phase in the composition of the ceramics.