Journal of the American Ceramic Society, Vol.97, No.5, 1434-1441, 2014
Luminescence and Quantum Efficiencies of Eu3+ -Doped Vanadate Garnets
Nondoped and 5.0mol% Eu3+-doped vanadate garnets Ca5Mg4(VO4)(6), NaCa2Mg2[VO4](3), KCa2Mg2[VO4](3), and NaSr2Mg2[VO4](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 NaCa2Mg2[VO4](3) and NaSr2Mg2[VO4](3) under excitation with UV light. These materials are suggested to be useful for lighting under the excitation with near-UV LED.