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

A process is reported for fiber crystal growth of (Tb,Yb)3Al5O12 from mixed Tb3Al5O12–Yb3Al5O12 melt using micro-pulling-down technique. A model which allow to predict segregation coefficients for different rare-earth cations 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 dodecahedral site in equal degree. Such an approximation was found to be applicable for the Tb3Al5O12–Yb3Al5O12 system. Therefore the uniform and macro defect free crystals were successfully grown from melt of about Tb2.2Yb0.8Al5O12 composition with a pulling down rate of up to 2 mm/min.