Influence of the isothermal annealing time on structural morphological, and photocatalytic characters of BiT/ZnWO4 composite

The abbreviated composite Bi4Ti3O12/ZnWO4 (BIT/ZW) was produced using the molten salt technique at 800°C. The impact of isothermal annealing time, in the second step, on the structural, morphological, and photocatalytic properties was investigated. X-ray diffraction (XRD) confirmed the formation of composites with varying proportions (76.8% BIT, 20.2% ZW), (71% BIT, 22.8% ZW), and (56.4% BIT, 36.6% ZW) at annealing times of 4, 6, and 8 hours at 950°C, respectively. A minor amount of pyrochlore phases (<7%) was observed. Increasing the annealing time affected the crystallinity of the composites. The crystallite size and grain size of BIT and ZnWO4 decreased with longer annealing times, leading to a reduction in the band gap from 2.95 to 2.83 eV. The composite (76.8% BIT, 20.2% ZW) exhibited photocatalytic activity that was two times higher for degrading methylene blue (MB) in the dark compared to the other composites, but showed an improvement in degradation under solar irradiation from 70% to 72.18%. The results indicate that annealing isothermal time can effectively modify the properties of the composites, creating a proven heterojunction between BIT and ZnWO4.