(Tb,Yb)(3)Al5O12 garnet: crystal-chemistry and fiber growth by micro-pulling-down technique

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.