Preparation and luminescent characteristics of Sr3RE2(BO3)4:Dy3+ (RE = Y, La, Gd) phosphors for white LED

Dysprosium-activated Sr3RE2(BO3)4 (RE = Y, La, Gd) phosphors were synthesized by a high temperature solid-state reaction method. The phase uniformity of the phosphors was characterized by X-ray powder diffraction (XRD) and the luminescence characteristics were investigated. The excitation spectra at 575 nm emission show strong spectral bands in the region of 300–500 nm. The emission spectra of the phosphors with 365 nm excitation show three bands centered at 484 nm, 575 nm and 680 nm, which originate from the transitions of 4F9/2 → 6H15/2, 4F9/2 → 6H13/2 and 4F9/2 → 6H11/2 of Dy3+, respectively. The effect of Dy3+ concentration on the emission intensity of the phosphors was investigated. The fluorescence decay curves for 4F9/2 → 6H13/2 excited at 365 nm and monitored at λem of 575 nm were measured. The decay times decreased slowly with increasing Dy3+ doping concentration due to a trap capturing to resonance fluorescence transfer of the activated ions and due to the exchange interactions between activated ion pairs. In order to determine the type of interaction between activated ions, the concentration dependence curves (lg(I/x) versus lg x) of Sr3RE2(BO3)4:Dy3+ (RE = Y, La, Gd) were plotted. The concentration quenching mechanism of the 4F9/2 → 6H13/2 (575 nm) transition of Dy3+ is the d–d interaction. All results indicate these phosphors are promising white-color luminescent materials.

Research highlights▶ Dysprosium-activated Sr3RE2(BO3)4 (RE = Y, La, Gd) phosphors were successfully synthesized by high temperature solid-state reaction method. ▶ The luminescence characteristics of UV-based Dy3+-activated Sr3RE2(BO3)4 (RE = Y, La, Gd) were detail investigated. ▶ The effect of Dy3+ concentration on the emission intensity of 4F9/2 → 6H13/2 (575 nm) transition under 365 nm excitation and the mechanism of concentration quenching were detail researched.