Synthesis, structural, band gap, and optical properties of Ba3(PO4)2 hierarchical structural materials

Ba 3 (PO 4 ) 2 structure with Rhombohedral phase was prepared by a facile wet chemical method. In this experiment, NaOH is used as a surfactant for various pH values. The prepared samples were analyzed using several analytical techniques such as XRD, SEM, EDX, UV–Visible absorption, and photoluminescence spectroscopy. Orthorhombic (BaHPO 4 ) phase appeared at pH7 and rhombohedral Ba 3 (PO 4 ) 2 phase formed at pH13 show that the pH value was very important factor for the final product formation and morphology. The phase changes have been monitored through the XRD data analysis. EDX analysis confirms the Ba:P ratios as 3:2. Band gap energy of synthesized microstructure was found to be 3.60 eV for rhombohedral phase (pH13) and 4.89 eV for orthorhombic phase (pH7), respectively. Significantly, the prepared sample at pH13, an intense blue light, emitted a narrow band in the broad band emission spectra, which have been explained from the transition of 3 T 1 → 1 A 1 in PO 4 3− ions. In the meantime, an apparent red shift was observed while changing the excitation wavelengths.