Control over the symmetry of the heat field in the station for growing LBO crystals by the Kyropoulos method

Dynamic control over the heat field during LBO crystal growth by High temperature solution method

“…Within the described furnace by varying the switching off time for each pair of heaters in the middle zone it is possible to displace the melt surface ''cold point'' in the crucible center. This procedure can be performed not only by measuring the radial temperature distribution, as described in [4], but also by observing the movement of small pieces of LBO ( $ 1-2 mm) thrown onto the flux surface at a temperature of 10-15 degrees higher than the equilibrium.…”

“…Stabilization of a ''cold point'' in the center of the crucible. That gives reliable seeding and growth of a ''symmetric'' crystal [4]. This point becomes more and more important with increment of the crucible diameter.…”

Automation of Crystal Growth from Melt

“…Instead, usually the force acting on a load cell connected to the seeding rod is used as the controlled variable [191,198]. Instead, usually the force acting on a load cell connected to the seeding rod is used as the controlled variable [191,198].…”

“…A common approach for controlling the Kyropoulos process is to numerically calculate the evolution of the temperature field in the furnace, which represents the desired growth of the crystal. [198]. Hence, one can apply a feed-forward control regime using these heater power trajectories.…”

Effect of power arrangement on the crystal shape during the Kyropoulos sapphire crystal growth process

“…For growing extra large crystals, the heater should have separate sections with different power inputs in order to control the thermal field in the melt during the growth process [13,14]. In the present study, global heat transfer and flow motion in a three-zone resistance heated KY furnace during the sapphire crystal crystallization process is investigated using the simulation process developed by Chen et al [11].…”