Structure and color-tunable luminescence properties of Sm3+ singly- and Dy3+/Sm3+ co-doped CaLaGa3O7 phosphors

Abstract

Sm³⁺ singly- and Dy³⁺/Sm³⁺ co-doped CaLaGa₃O₇ phosphors were synthesized successfully by a traditional high-temperature solid-state reaction method. Their structure was determined by X-ray diffraction (XRD) measurements, confirming the tetragonal phase of the samples with space group P $\bar{4}$ 2₁m. For Sm³⁺: CaLaGa₃O₇ samples, the excitation spectra show that the phosphors could be excited by 403 nm light. The strongest emission peak is at 598 nm, which is assigned to the transition from Sm³⁺: ⁴G_5/2 level to ⁶H_7/2 state. The CIE color coordinate with optimal Sm³⁺ doping concentration was calculated to be (0.5882, 0.4110), which is located in the orange-red area. For Dy³⁺/Sm³⁺: CaLaGa₃O₇ phosphors, the excitation spectra show that the obtained samples could be effective pumped by 348 nm or 403 nm. Regardless of the excitation wavelength, the emission spectrum contains the characteristic emission peaks of Dy³⁺ and Sm³⁺. The relative emission intensity of Dy³⁺ and Sm³⁺ could be adjusted by modifying the concentration of Sm³⁺ and the exciting wavelength, indicating that the luminescence color is tunable for Dy³⁺/Sm³⁺ co-doped samples. The luminescence performance and fluorescence lifetime jointly prove that mutual energy transfers between Dy³⁺ and Sm³⁺ take place in the Dy³⁺/Sm³⁺: CaLaGa₃O₇ phosphors. The CIE color coordinates and correlated color temperature were calculated for varying rare-earth concentration as well as excitation wavelength to ascertain their potential applications in light emission devices.