Luminescence and Quantum Efficiencies of Eu3+‐Doped Vanadate Garnets

Nondoped and 5.0 mol% Eu³⁺‐doped vanadate garnets Ca₅Mg₄(VO₄)₆, NaCa₂Mg₂VO₄]₃, KCa₂Mg₂VO₄]₃, and NaSr₂Mg₂VO₄]₃ were synthesized by solid‐state reactions. The formation of single‐phase compound with garnet structure is confirmed by X‐ray diffraction. The photoluminescence (PL) and PL excitation (PLE) spectra are investigated together with color coordinates. The luminescence process is discussed on the charge‐transfer transitions in VO₄]^3? ions and the crystal structure. The PL quantum efficiencies (QE) are measured for nondoped and Eu³⁺‐doped samples. The Eu³⁺‐doped samples have higher QEs than the corresponding nondoped ones although the energy transfer occurs from VO₄]^3? to Eu³⁺. Broad emission band due to VO₄]^3? with intense sharp lines due to Eu³⁺, which gives white color, is observed in Eu³⁺‐doped NaCa₂Mg₂VO₄]₃ and NaSr₂Mg₂VO₄]₃ under excitation with UV light. These materials are suggested to be useful for lighting under the excitation with near‐UV LED.