Photoinduced Preparation of Bandgap-Engineered Garnet Powders

The indirect photochemical synthesis for the preparation of bandgap- or defect-engineered multicomponent garnet powders from aqueous solutions was investigated. Gd
₃
(Ga,Al)
₅
O
₁₂
(GGAG) doped with Ce or Ce + Eu and Lu
₃
(Al,Sb)
₅
O
₁₂
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 Ce
³⁺
5
d
-
$4f$
emission. To induce the formation of Ce
⁴⁺
ions as defects competing with electron traps, Mg
²⁺
ions were added into the solutions and calcination in air was examined. Both factors were shown to cause the decrease of Ce
³⁺
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 Sb
₂
O
₃
evaporation during calcination.