Transparent Ce~(3+):GdYAG ceramic phosphors for white LED

摘要

Transparent Ce:GdYAG ceramics were synthesized from the oxide powder produced by a co-preparation method in the composition of (Gd_γY_(0.999-γ)Ce_(0.001)_3Al_5O_(12). The sample showed transparency as high as 80 % at 800 nm. A broad emission band of Ce3+: 5d-*4f transition shifted from 530 nm to 560 nm with increasing Gd content. The color coordinates (x, y) under blue LED excitation and quantum yield (QY) were evaluated with an integrating sphere. The color coordinates of the sample under blue LED excitation were increased with increasing thickness. By substituting Gd~(3+) for Y~(3+), the color coordinates also shifted to lower right and became closer to the Planckian locus in the chromaticity diagram. The red shift was explained by the energy change of 5d level of Ce~(3+) by the substitution of Gd~(3+) for Y~(3+). With increasing excitation wavelength, the color coordinates of the γ=0 sample shifted from blue to yellow. This result is related to the shape of excitation band of the sample. The QY of the γ=0 sample was almost excitation wavelength independent in the range of 400 ~470 nm.