Remarkable structure and luminescence regulation of a Gd2LuAl5O12:Ce garnet phosphor with a Ca2+/Si4+ pair for high-quality w-WLED lighting

Abstract

Doping Gd₂LuAl₅O₁₂:Ce with a Ca²⁺/Si⁴⁺ pair produced a series of Gd_1.97−xLuCa_xAl_5−xSi_xO₁₂:0.03Ce (x = 0.0–1.2) garnet new phosphors, and remarkable regulation of the crystal structure and Ce³⁺ luminescence was achieved. Rietveld refinement and spectral analysis revealed that greater incorporation of Ca²⁺/Si⁴⁺ led to a higher lattice rigidity by cell contraction, a narrower bandgap, a longer average bond length/less distortion of the [CeO₈] dodecahedron and decreased centroid shift/crystal field splitting of the Ce³⁺ 5d energy level. A blue-shifted 4f–5d₁ transition, a narrower emission band, improved thermal stability of luminescence and a shorter fluorescence lifetime were observed with increasing Ca²⁺/Si⁴⁺ content. Applying the yellowish-green-emitting Gd_0.77LuCa_1.2Al_3.8Si_1.2O₁₂:0.03Ce optimal phosphor (x = 1.2), together with a commercial CaAlSiN₃:Eu red phosphor, in 450 nm-excited LED lighting produced a low CCT of ∼3625 K and a high CRI/R9 of ∼95.2/94.8, indicating that the phosphor has application potential in high-performance w-WLED.