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. Based on the results and the structural model obtained from CLGO (ICSD: 109444), XRD Rietveld refining was performed, which confirmed the tetragonal phase of the samples with space group P[[EQUATION]]21m. Then, the luminescence properties and energy transfer process between Dy3+ and Sm3+ were studied. For Sm3+: CaLaGa3O7 samples, the excitation spectra show that the phosphors could be excited by 403 nm light. The emission spectra include four emission peaks centered at 561, 598, 644 and 707 nm, which are assigned to the transitions from Sm3+: 4G5/2 level to 6H5/2, 6H7/2, 6H9/2 and 6H11/2, respectively. Among them, the strongest emission peak is at 598 nm, which belongs to partially magnetic dipole and partially forced electric dipole transition. The CIE color coordinate with optimal Sm3+ doping concentration was calculated to be (0.5882, 0.41096), which is located in the orange-red area. For Dy3+/Sm3+: CaLaGa3O7 phosphors, the excitation spectra show that the Dy3+/Sm3+ co-doped 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+. More importantly, 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. Further, the variation of the lifetime was studied in detail. The luminescence performance and fluorescence lifetime jointly prove that mutual energy transfers between Dy3+ and Sm3+ take place in the Dy3+/Sm3+: CaLaGa3O7 phosphors. Moreover, 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.

Keywords: phosphors, Dy3+/Sm3+: CaLaGa3O7, Structure, Energy transfer, Color-tunable properties