X-ray and optical studies of ytterbium-doped gallium garnets

Single crystals of yttrium gallium and lutetium gallium garnets doped with ytterbium were grown from the melt by Czochralski technique. Comparison is made between the lattice spacing of ceramic and single crystals to estimate the degree of octahedral ytterbium substitution. When heated to around 1200°C under reducing atmosphere the yttrium gallium garnet crystal acquires violet color due to appearance of additional absorption bands. Displacements of absorption bands as a function of the average radius on the dodecahedral site resemble those observed in aluminum garnets and generally considered as associated with divalent ytterbium. Basing on X-ray calibration, the peak positions of induced absorption bands can be used to estimate the dodecahedral concentration of ytterbium in the crystal. Charge transfer luminescence properties were studied in LuGG:Yb crystals.