Effect of TiO${}_2$ doping on structural and optical properties of CdSZn${}_3$(PO${}_4$)${}_2$ nanocomposites

Pure and (0.3, 0.6 and 0.9 mol%) TiO${}_2$-doped CdSZn${}_3$(PO${}_4$)${}_2$ semiconducting nanocomposites were successfully synthesized by hydrothermal route. The structural compositions, surface morphology, diffuse reflectance spectroscopy and luminescence properties of all the nanocomposites were systematically investigated. X-ray diffraction pattern exhibits the co-existence of both hexagonal phase of CdS and a mixer of γ and β monoclinic Zn${}_3$(PO${}_4$)${}_2$ phases with high crystalline order. Upon increasing of TiO${}_2$ content from 0.3 to 0.9 mol%, γ-Zn${}_3$(PO${}_4$)${}_2$ phase is decreasing while β-Zn${}_3$(PO${}_4$)${}_2$ phase is found to increase. Further, it has been found that the TiO${}_2$ additive atoms did not segregate to form secondary phases but led to variation in grain size, local disorder and local strain in the nanocomposites. The average crystallite size of nanocomposites is in the range 22–25 nm. The surface morphology of the samples was clearly shown as flakes surrounded by hexagonal CdS spheres like heterostructure type morphology. EDAX results confirm the stoichiometry of all the samples with slight variation of CdS content with increasing TiO${}_2$ dopant content. Optical band gap values are found to decrease from 2.52 to 2.44 eV with increasing TiO${}_2$ content. Further, photoluminescence studies revealed that all the samples exhibited strong fluorescence in the visible wavelength region and the chromaticity characteristics from CIE diagram were also explored in search of their applicability for commercial LED applications.