Visible Luminescence of Rare-Earth Yttrium Gallium Garnets

Yttrium gallium garnet (${\mathrm{Y}}_3$ ${\mathrm{Ga}}_5$ ${\mathrm{O}}_{12}$) has been prepared with small percentages of different rare earths substituted for yttrium. Garnets activated with Pr, Sm, Eu, Tb, Dy, Ho, Er, and Tm are all luminescent. The emission and excitation spectra of the samples have been measured at 77°K. The data have been analyzed in terms of the atomic energy levels of the impurity ions and the effects of crystalline field and of phonon interactions. Wherever possible, comments are made about whether the crystal field can be treated as possessing cubic or lower symmetry.