Production and optical properties of Ce3+‐activated and Lu3+‐stabilized transparent gadolinium aluminate garnet ceramics

We first report the novel Ce3+-activated and Lu3+-stabilized gadolinium aluminate garnet (GAG) transparent ceramics derived from their precipitation precursors via a facile co-precipitation strategy using ammonium hydrogen carbonate (AHC) as the precipitant. The resulting precursors in liquid phase were substantially homogeneous solid solutions and could directly convert into sinterable garnet powders via pyrolysis. Substituting 35 at.% of Lu3+ for Gd3+ was effective to stabilize the cubic GAG garnet structure and transparent (Gd,Lu)(3)Al5O12:Ce ceramics were successfully fabricated by vacuum sintering at 1715 degrees C. The ceramic transparency was improved by optimizing the particle processing conditions and the best sample had an in-line transmittance of similar to 70% at 580 nm (Ce3+ emission center) and over 80% in partial infrared region with a fine average grain size of similar to 4.5 mu m. Transparent (Gd,Lu)(3)Al5O12:Ce ceramics have a short critical wavelength (<200 nm) and a maximal infrared cut-off at similar to 6.6 mu m. Both the (Gd,Lu)(3)Al5O12:Ce phosphor powder and the transparent ceramic exhibited characteristic yellow emission of Ce3+ with strong broad emission bands from 490 to 750 nm upon UV excitation into two groups of broad bands around 340 and 470 nm. The photoluminescence and photoluminescence excitation intensities as well as the quantum yield were greatly enhanced via high-temperature densification. Both the phosphor powder and ceramic bulk had short effective fluorescence lifetimes.