Near-ultraviolet excited Tm3+ and Dy3+ ions co-doped barium lanthanum silica oxide phosphors for white-light applications

Abstract

Nowadays, trivalent rare-earth ions activated inorganic luminescent materials have been widely investigated owing to their important applications in solid-state lighting field. Tm3+ and Dy3+ ions single- or co-doped Ba3La6(SiO4)6 (BLSO) phosphor materials for white light application were synthesized by a citrate-based sol-gel method. The prepared samples were examined by X-ray diffraction (XRD), scanning electron microscopy and Fourier-transform infrared spectroscopy to analyze the phase purity, surface morphology and existence of functional groups, respectively. The XRD pattern confirmed that the BLSO host lattice exhibited a hexagonal crystal structure with P63/m (176) space group, which is well indexed with standard JCPDS data. From photoluminescence results, the BLSO:Tm3+ phosphors exhibited purplish blue emission at 453 nm (1D2→3F4) and the BLSO:Dy3+ phosphors showed predominant yellow emission at 575 nm (4F9/2 → 6H13/2) compared to their shoulder blue emission at 479 nm (4F9/2 → 6H15/2), indicating that the Dy3+ ions occupied lattice sites with low inversion symmetry. The determined Commission Internationale de I’Eclairage (CIE) (0.3391, 0.3302) values for the Tm3+/Dy3+ co-doped BLSO phosphors were near to the standard sun light CIE values (0.33, 0.33) under near-ultraviolet (364 nm) excitation. The energy transfer process from Dy3+ to Tm3+ ions was discussed and it was proved by their corresponding decay curves. Additionally, thermal study was carried out for the optimized phosphor and it maintained superior thermal PL properties.