RE-Doped Ternary Sulfides ALnS2 (A = Rb, K, Na; Ln = La, Gd, Lu, Y) - a New Phosphor Family

We have recently started to investigate structural, scintillation, luminescence and paramagnetic (in case of Eu²⁺ doping) properties of the unexplored family of rare earth (RE)-doped ternary sulfides of general formula ALnS₂ (A = Rb, K, Na; Ln = La, Gd, Lu, Y), which show prospective application potential in the field of X-ray and solid state white LED phosphors. The X-ray diffraction (XRD) detected only a single crystalline phase of rhombohedral lattice system, except NaLaS₂ which has cubic structure. Time-resolved luminescence spectroscopy, XRD and electron paramagnetic resonance were employed to understand the nature of Eu²⁺ emission centre in these sulfidic hosts and find correlation between structural and optical properties of these materials. Eu²⁺ and Ce³⁺ emission features are investigated in a broad temperature and concentration ranges and phenomenological modeling and delayed recombination decay measurements are used to understand better the Eu²⁺ excited state dynamics. Optical properties of ALnS₂ doped by another RE ions are presented as well. Motivating figure 1 shows clear energy shift of the Eu²⁺ emission spectra maxima with different chemical compositions, peaking from 498 nm (RbLuS₂) to 779 nm (NaGdS₂).

Figure 1. RT Radioluminescence spectra of Eu²⁺-doped ALnS₂.