Tb-doped Yb3Al5O12 and Y3Al5O12 single crystals were grown by the micropulling-down method in the form of rods of 2 mm diameter and a few cm in length. Emission spectra and decay times of Tb3+ luminescent centers were measured for Tb concentrations in a Y(Yb) sublattice of (1-70) %. A noticeable decrease of the emission intensity and decay time was obtained for Tb concentrations above 15% and 30% for Y3Al5O12 and Yb3Al5O12 hosts, respectively. Both effects are ascribed to the concentration quenching of Tb3+ luminescence due to energy migration over the Tb3+ subsystem and subsequent energy transfer to unspecified nonradiative traps. Energy migration process and structural aspects are discussed.

Keywords: micropulling-down crystal growth, luminescence, rare earth ions, concentration quenching