Monoclinic Lu_2–<i>x</i>Sm_<i>x</i>WO₆‑Based White Light-Emitting Phosphors: From Ground–Excited-States Calculation Prediction to Experiment Realization

Through ground state and constrained density function calculations, Sm³⁺ ions luminescence in self-activated monoclinic Lu₂WO₆ was originated from intra 4f → 4f transitions, not inter 5d → 4f transitions. Theoretically the white luminescence was obtained by combining red and blue-green emissions of 4f energy levels and W–O charge transfer transitions. Experimentally, pure and Sm³⁺ doping Lu₂WO₆ powders were synthesized using solid phase reaction calcined in air atmosphere. By the analysis of X-ray photoelectron spectroscopy and Rietveld refinement, element Sm charge state was trivalent, and Sm³⁺ doping was concentration-dependent selectively doping in three Lu sites. With the increase of Sm³⁺ concentrations, the color coordinates changed gradually from blue (0.17, 0.17) through white light (0.33, 0.25) toward orange (0.44, 0.32) in the visible spectral under 325 nm excitation. On the basis of the theoretical prediction and experimental preparation, a white emission LED lamp was produced using a 365 nm ultraviolet chip and Lu_1.99Sm_0.01WO₆ phosphor. The present design method can be applied to select excellent activators from a large number of rare-earth (Re) ions like Sm³⁺ and Eu^3+/2+ or non-Re ions like Bi³⁺ and Mn⁴⁺ in various matrixes