HEAT-TRANSFER AND INTERFACE INVERSION DURING THE CZOCHRALSKI GROWTH OF YTTRIUM-ALUMINUM-GARNET AND GADOLINIUM GALLIUM GARNET

Computer-aided simulations are performed using an integrated process m odel for the Czochralski (CZ) growth of yttrium aluminum garnet (YAG) and gadolinium gallium garnet (GGG). Internal radiant heat transfer th rough the crystal is responsible for the deeply convex melt/crystal in terface and the propensity for crystal cracking with large cone angles during CZ YAG growth. The nature of interface inversion by crystal ro tation is fundamentally different for YAG growth under low and high th ermal gradients. Results suggest that classical ''flat-interface'' gro wth via crystal rotation is attainable for YAG growth only under low-g radient thermal conditions, while this limitation is not as stringent for the growth of GGG. The depth of the melt is also shown to affect i nterface inversion for GGG. The complicated dependence of interface in version on many system details, rather than solely crystal rotation, s uggests that this effect is not adequately described by simple, univer sal scalings which have been previously proposed.