The effects of Mg2+/Si4+ substitution on crystal structure, local coordination and photoluminescence of (Gd,Lu)(3)Al5O12:Ce garnet phosphor

摘要

A series of phase-pure [(Gd0.6Lu0.4)(1-y)Ce-y](3)[Al1-z(Mg/Si)(z)](5)O-12 (y = 0-0.012, z = 0-0.15) garnet phosphors were synthesized via gel-combustion, and the effects of Mg2+/Si4+ substitution on characteristics of the garnet host and Ce3+ luminescence were investigated in detail. The maximum amount of equimolar Mg2+/Si4+ dopants that can be incorporated into the garnet lattice and the optimal Ce3+ content for luminescence were determined to be around z = 0.15 and y = 0.010, respectively. Mg2+/Si4+ codoping was analyzed to narrow bandgap of the host, non-uniformly compress the [CeO8] dodecahedron, enlarge the [Al-O] polyhedrons and meanwhile alter bond angles. Increasing Mg2+/Si4+ content was found to lower the intensity, fluorescence lifetime and thermal stability of Ce3+ luminescence and meanwhile red-shift the 4f-5d(1) excitation/emission peaks. The results were interpreted by considering band structure and crystal field splitting of the Ce3+ 5d energy level. The y = 0.01 and z = 0.15 phosphor exhibited a broad emission peaked at similar to 561 nm under 457 nm excitation, with CIE color coordinates of around (0.449,0.527), a correlated color temperature of similar to 3567 K, a fluorescence lifetime of similar to 43 ns, and an activation energy for thermal quenching of similar to 0.267 eV. Electroluminescence indicated that the phosphors may find potential application in warm-white LEDs excited by blue-LED chips. (C) 2019 Elsevier B.V. All rights reserved.