Synthesis, structure, and luminescence properties of melilite Dy3+:Lu CaLa0.98–Ga3O7 phosphors for use in yellow light-emitting devices

Dy3+ and Lu3+ co-doped CaLaGa3O7 phosphors were prepared via high-temperature solid-phase reaction. The electronic structures of LuxCaLa0.98–xGa3O7 were investigated by the first-principles calculations for the first time. The influence of Lu3+ on yellow light emission was studied using X-ray diffraction (XRD) and photoluminescence (PL) measurements. The XRD results indicate that compared to Dy3+:CaLaGa3O7, the cell parameters of Dy3+:LuCaLaGa3O7 tend to decrease, which is due to the smaller radius of Lu3+. When pumped by blue GaN laser diode (LD), the emission peaks of phosphors with different Lu3+ doping concentrations in the visible region are similar, with the strongest peak at 574 nm in the yellow light region, which is sensitive to human eyes. The optimal doping concentration of Lu3+ is confirmed to be 1 at%, when all emission spectra and measured fluorescence lifetimes are taken into account. Moreover, the optimal phosphor composition Dy3+:LuxCaLa0.98–xGa3O7 (x = 0.01) has an internal quantum efficiency (IQE) of 46.94% and an external quantum efficiency (EQE) of 15.19%. Most notably, the prepared phosphor demonstrates excellent thermal stability and a high activation energy (0.203 eV). In addition, the International Illumination Commission color coordinates of the Dy3+:LuxCaLa0.98–xGa3O7 phosphors are in the yellow light area. The above analysis indicates that the Dy3+:LuxCaLa0.98–xGa3O7 (x = 0.01) phosphor has promising application prospects in yellow light-emitting devices.