Crystal structural and photoluminescence properties of Eu3+ doped MgZn2(PO4)2 phosphors by R+ (R = Li, Na, K) charge compensation

Abstract

Eu³⁺ single doping and Eu³⁺, R⁺ (R = Li, Na, K) charge compensation co-doped orange-red MgZn₂(PO₄)₂ phosphors were prepared by high-temperature solid-state method. The effect of charge compensation agent R⁺ on the luminescence properties of MgZn₂(PO₄)₂:Eu³⁺ phosphors was investigated. The morphology and composition of the samples were characterized using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), high-angle annular dark field (HAADF), and energy dispersive spectroscopy (EDS) techniques. The photoluminescence properties were studied using excitation and emission spectra. In this study, R⁺ is used as charge compensation to improve the emission intensity of Eu³⁺ and the physical explanation is given. The optimal doping concentration of Eu³⁺ in MgZn₂(PO₄)₂ was obtained to be 5 mol%. Under ultraviolet (396 nm) excitation, a strong orange-red luminescence corresponding to the ⁵D₀ → ⁷F_i (i = 1, 2, 3, and 4) transition of Eu³⁺ is observed. The CIE coordinates and decay lifetimes of typical samples are discussed. The chromaticity coordinates of the two samples were (0.604, 0.392) and (0.616, 0.382), respectively, both located in the orange-red region. The fluorescence lifetime of MgZn₂(PO₄)₂ phosphors co-doped 5% Eu³⁺ and 5% R⁺ (R = Na and K) is obviously improved. The results show that MgZn_1.9R_0.05(PO₄)₂:0.05Eu³⁺ (R = Na and K) is a kind of orange-red phosphor with high efficiency under near ultraviolet excitation.