Heat transfer in growing Bi 4Ge 3O 12 crystals under weak convection: II—radiative–conductive heat transfer

Abstract

Experimental and calculation investigations of the features of radiative–conductive heat transfer during the growth of bismuth germanate (Bi 4Ge 3O 12) single crystals are carried out. It is demonstrated that due to the radiative–conductive character of heat transfer, the temperature regime of the crystallization of perfect crystals has non-conventional character. In order to keep the growth rate constant during crystal growth under condition of weak thermal convection, it is necessary to decrease the seed temperature at the beginning of growth; then temperature should be kept constant; and finally, starting from a certain length of the crystal ( L cr≈30 mm), seed temperature should be slightly increased. It is shown that the presence of defects in crystal decreases L cr value. The strong effect of supercooling of the interface on the features of heat transfer during the growth of Bi 4Ge 3O 12 crystals is demonstrated.