Site-selective and cooperative doping of GdAlO:Ce garnets for structural stabilization and warm WLED lighting of low CCT and high CRI.

Synergistic doping of the metastable GdAlO:Ce garnet with a Ca/Hf pair and Sc to form GdCaHfScAlO:0.03Ce ( = 0.5-2.0, = 0.0-1.5, + = 2.0) solid solution was conducted for the structural stabilization and photoluminescence manipulation. The site selection of Ca/Hf/Sc dopants and the effects of doping on the crystal structure, local coordination, band structure and Ce luminescence were revealed in detail with the results of XRD, Rietveld refinement, TEM, and UV-Vis/photoluminescence spectroscopy. A decrease in Ca/Hf and an increase in the Sc content were observed to shrink the lattice, widen the bandgap of the garnet host, red-shift the excitation/emission wavelength, broaden the emission band and shorten the fluorescence lifetime of Ce. The spectral changes were rationalized by considering the local coordination and crystal field splitting of the Ce 5d energy level. Application of typical GdCaHfAlO:0.03Ce ( = 2.0, = 0) cyan and GdCaHfScAlO:0.03Ce ( = 0.5, = 1.5) greenish-yellow phosphors in w-WLED lighting produced low correlated color temperatures of ∼3842 and 3514 K, high color rendering indices of ∼88 and 93 and favorable luminous efficacies of ∼32.9 and 14.7 lm/W under the excitation of 395 nm n-UV and 450 nm blue LED chips, respectively.