Photoinduced Preparation of Bandgap-Engineered Garnet Powders

Abstract

The indirect photochemical synthesis for the preparation of bandgap- or defect-engineered multicomponent garnet powders from aqueous solutions was investigated. Gd3(Ga,Al)5O12 (GGAG) doped with Ce or Ce + Eu and Lu3(Al,Sb)5O12 doped with Eu were produced by calcination of the prepared solid precursors at various conditions and their structural and luminescence properties including decay curves were thoroughly studied. In GGAG:Ce, the content of Ga was shown to have strong impact on the lattice parameter and position of the Ce3+ 5 d - $4f$ emission. To induce the formation of Ce4+ ions as defects competing with electron traps, Mg2+ ions were added into the solutions and calcination in air was examined. Both factors were shown to cause the decrease of Ce3+ emission intensity and acceleration of luminescence decay in a similar way. The doping with Sb(III) required calcination of solid precursors in inert atmosphere to prevent formation of an unknown pyrochlore-type phase containing Sb(V). Low temperatures were needed to limit Sb2O3 evaporation during calcination.