This work synthesizes and comprehensively characterizes a series of yavapaiite-type phosphates, BaSb_xCr_xTi_1-2x(PO₄)₂, for x values ranging from 0 to 0.5, using a solid-state reaction method. Clarifying the structural and optical changes brought about by partially replacing titanium (Ti) with antimony (Sb) and chromium (Cr) was the main goal. The crystal structures of these compounds were characterized using X-ray diffraction (XRD) methods in addition to Rietveld refinement. The compounds were discovered to have a monoclinic structure in the C2/m space group. Extensive studies were carried out to examine the impact of Sb/Cr substitution on angles and lattice characteristics. Vibrational properties were investigated using infrared (IR) spectroscopy, which revealed distinct bands linked to the PO₄^3- tetrahedral units . The optical properties were revealed by UV-visible absorption spectroscopy, which also showed how the inclusion of Sb and Cr atoms affected the optical band gap. It was discovered that the direct band gap values ranged from 1.3 to 3.1 eV, suggesting a tunable semiconducting behavior dependent on the particular Sb/Cr ratio.
Density Functional Theory (DFT) calculations were carried out to strengthen this basis in order to comprehend the electronic structure and precisely anticipate the optical characteristics of these phosphates. The DFT analyses provided further insights into the band structure alterations resulting from the Sb/Cr substitution, confirmed the experimental results. These computer calculations gave rise to a microscopic perspective of the electronic transitions responsible for the semiconducting behavior, as well as validating the observed variations in the optical band gap.

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