A process is reported for fiber crystal growth of (Tb,Yb)(3)Al5O12 from mix
ed Tb5Al5O12-Yb3Al5O12 melt using micro-pulling-down technique. A model whi
ch allow to predict segregation coefficients for different rare-earth catio
ns in mixed garnet crystals is reported, its key feature being a selection
of couple of the cations which do not fit to the equilibrium size of the do
decahedral site in equal degree. Such an approximation was found to be appl
icable for the Tb3Al5O12-Yb3Al5O12 system. Therefore the uniform and macro
defect free crystals were successfully grown from melt of about Tb2.2Yb0.8A
l5O12 composition with a pulling down rate of up to 2 mm/min. (C) 2000 Publ
ished by Elsevier Science S.A. All rights reserved.