Experimental and numerical effects of active afterheater addition on the growth of langatate (La3Ga5.5Ta0.5O14) crystals by the Czochralski method

The Czochralski (Cz) technique under an argon/oxygen atmosphere has been used to grow 35 mm diameter La3Ga5.5Ta0.5O14 langatate (LGT) crystals along the Z-axis. Addition of an afterheater is proposed to improve the growth and crystal properties. Two furnace configurations, without and with an afterheater, are investigated experimentally and numerically. A global model for the entire furnace was used in investigating the mechanism of flow, heat transfer, melt-crystal interface shape and 3-d thermal stress considering the crystal anisotropy. Addition of the afterheater changes considerably the thermal field in the growth atmosphere. A decrease of 56% of the maximum von Mises stress and 30% of the interface convexity are found through the use of the afterheater. Experimentally, a more stable growth has been achieved and this resulted in a good quality crystal.