Theoretical and experimental investigation of Gd3+-doped white light-emitting chlorapatite Ca6Na2Y2(SiO4)6Cl2 synthesized by hydrothermal route

A series of white light-emitting Ca6-xNa2Y2(SiO4)6Cl2:Gd3+ chlorapatite compounds were synthesized by liquid solid solution-based hydrothermal method. The structural, electronic and optical properties of synthesized chlorapatite were studied in detail. The X-ray diffraction (XRD) analysis confirms the formation of monoclinic structure with space group P21/c. Fourier transform infrared spectroscopy shows different modes of SiO4 tetrahedron, with no impurity peaks due to (OH) and (CO2) group. Theoretical calculations were done by B3LYP hybrid GGA approximation using density functional theory. The computational band gap value of 3.8 eV was calculated using 3 × 3 × 3 Monkhorst mesh, which satisfies the experimental value of 4.3 eV calculated by diffuse transmittance spectroscopy. The band gap value calculated by molecular orbital theory was found to be 4.01 eV, which satisfied the above results. Mulliken population analysis shows that Y bonds are more covalent in nature as compared to Ca and Na bonds. The photoluminescence emission peaks obtained at 468 nm, 482 nm, 492 nm, 549 nm and 661 nm are perceived due to 6G7/2 – 6DJ, 6G7/2 – 6IJ and 6PJ – 8S7/2 transitions in white region under 220 nm UV excitation.