Effect of monovalent charge compensators on the photoluminescence properties of Ca3(PO4)2:Tb3+, A+ (A = Li, Na, K) phosphors

Abstract

Ca3-x(PO4)2:xTb3+ (0.2 ≤ x ≤ 0.4), Ca2.3(PO4)2:0.35Tb3+, 0.35A+ (A = Li, Na, K), and Ca2.3(PO4)2:0.35Tb3+, yLi+ (0.35 ≤ y ≤ 0.455) phosphors were prepared by solid-state reaction. All the prepared phosphors formed a rhombohedral unit cell with the R3c space group. To improve the photoluminescence (PL) properties of the Ca2.65(PO4)2:0.35Tb3+ phosphor, monovalent charge compensators such as Li+, NA+, and K+ were added to the Ca2.65(PO4)2:0.35Tb3+ phosphor. The charge compensators acted as fluxes, so they improved the crystallinity. The excitation and emission properties were significantly improved through the incorporation of charge compensators. In particular, among the charge compensators, Li+ ion substantially enhanced the emission intensity and color purity. Furthermore, considering the evaporation of Li2CO3 during the annealing process, we optimized the concentration of Li+ charge compensator to enhance its PL performance. Impressively, the green emission intensity of the Ca2.3(PO4)2:0.35Tb3+, 0.385Li+ phosphor was 260 % higher than that of the Ca2.65(PO4)2:0.35Tb3+ phosphor. We believe that the effect of charge compensators on the PL properties and the optimum concentration of Li+ charge compensator are useful for the design of phosphors in light-emitting diodes.