Production and optical properties of Ce 3+ ‐activated and Lu 3+ ‐stabilized transparent gadolinium aluminate garnet ceramics

We first report the novel Ce 3+ ‐activated and Lu 3+ ‐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 Lu 3+ for Gd 3+ was effective to stabilize the cubic GAG garnet structure and transparent (Gd,Lu) 3 Al 5 O 12 :Ce ceramics were successfully fabricated by vacuum sintering at 1715°C. The ceramic transparency was improved by optimizing the particle processing conditions and the best sample had an in‐line transmittance of ~70% at 580 nm (Ce 3+ emission center) and over 80% in partial infrared region with a fine average grain size of ~4.5 μm. Transparent (Gd,Lu) 3 Al 5 O 12 :Ce ceramics have a short critical wavelength (<200 nm) and a maximal infrared cut‐off at ~6.6 μm. Both the (Gd,Lu) 3 Al 5 O 12 :Ce phosphor powder and the transparent ceramic exhibited characteristic yellow emission of Ce 3+ 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.