Blue and green emissions with high color purity from nanocrystalline Ca2Gd8Si6O26:Ln (Ln = Tm or Er) phosphors

Blue and green light emissive nanocrystalline Ca₂Gd₈Si₆O₂₆ (CGS):Tm³⁺ and CGS:Er³⁺ phosphors with high color purity were prepared by solvothermal reaction method. The structural and morphological properties of these phosphors were evaluated by the powder X-ray diffraction (XRD) and scanning electron microscopy, respectively. From the XRD results, Tm³⁺:CGS and Er³⁺:CGS phosphors had the characteristic peaks of oxyapatite in the hexagonal lattice structure. The visible luminescence properties of phosphors were obtained by ultraviolet (UV) or near-UV light and low voltage electron beam (0.5-5 kV) excitation. The photoluminescence and cathodoluminescence properties were investigated by changing the variation of Tm³⁺ or Er³⁺ concentrations and the acceleration voltage, respectively. The CGS:Tm³⁺ phosphors exhibited the blue emission due to ¹D₂→³F₄ transition, while the CGS:Er³⁺ phosphors showed the green emission due to ⁴S_3/2→⁴I_15/2 transition. The color purity and chromaticity coordinates of the fabricated phosphors are comparable to or better than those of standard phosphors for lighting or imaging devices.