by doing this the stress induced birefringence and small angle grain boundaries can be reduced the solid liquid interface can be constrained within the insulation zone by appropriately choosing the temperature set points of the melting chamber 114 and the annealing chamber 116 the axial temperature gradient is largely controlled by the temperatures of the melting chamber 114 and the annealing chamber 116 as well as the configuration of the furnace 112 the length of the insulation diaphragm 124 zone and the material and size of the crucible 104 for the temperature gradient at the solid liquid interface 134 the growth velocity also has an effect the temperature gradient in the crystal tends to increase with the growth velocity due to the latent heat released during solidification however this effect could be negligible if the translation speed of the crucible 104 during crystal growth is below 3 mm hr preferably the translation speed of the crucible 104 is in a range from 0 5 mm hr to less than 3 mm hr preferably the translation speed does not vary by more than 0 1 mm hr for illustration purposes 300 mm diameter 110 and 100 oriented caf 2 crystal growth experiments were carried out separately in a vertical bridgman furnace the feedstock was first mixed with scavengers and then put in a graphite crucible with a 110 oriented caf 2 seed crystal for 110 crystals and a 100 oriented caf 2 seed crystal for 100 crystals the axial temperature gradient and the growth rate were set at around 6 u00b0 c cm and less than 3 mm hr respectively under these growth conditions 110 and 100 oriented single crystals were successfully obtained the crystals were cooled down using a conventional annealing process typically including a rapid.