Ionic liquid-assisted hydrothermal synthesis and luminescence properties of Na_3Y_(1-x)(PO_4)_2: xTb~(3+) phosphors

摘要

In this study, a series of spindle-like Na_3Y_(1-x)(PO_4)_2: xTb~(3+) phosphors have been controllably synthesized by an ionic liquid-assisted hydrothermal route. The structures and morphologies of the as-synthesized products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Photolu-minescence spectroscopy (PL), fluorescence decay, and temperature-dependent emission spectroscopy were adopted to characterized the luminescence properties of the samples. The excitation spectra of Na_3Y_(1-x)(PO_4)_2: xTb~(3+) comprised several well-resolved absorption bands at 273, 285, 304, 318, 340, 352, 368, and 378 nm. When excited at 368 nm, Na_3Y_(1-x)(PO_4)_2: xTb~(3+) phosphors could exhibit emission bands at 490 nm (~5D_4 → ~7F_6), 545 nm (~5D_4 → ~7F_5), 586 nm (~5D_4 →~7F_4), and 624 nm (~5D_4→~7F_3), respectively. The concentration quenching occurred when x is beyond 0.22. The decay time of the photoluminescence of Na_3Y_(1-x)( PO_4)_2: xTb~(3+) decreased with the increase of Tb~(3+) doping, which demonstrated the existence of energy transfer among Tb~(3+) ions. The Commission Internationale de L'Eclairage (CIE) chromaticity coordinates of Na_3Y_(0.78)(PO_4)_2: 0.22Tb~(3+) were (0.3273, 0.5199) at 273 K, which located in the green region. The temperature dependence experiments revealed that the title material had excellent luminescence thermal stability. The luminescence intensity of Na_3Y_(0.78)(PO_4)_2: 0.22Tb~(3+) phosphor at 473 K declined 22.1% to its initial intensity. The title material could be used as green light-emitting phosphor for cold white LED applications.