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

• Published in: Journal of crystal growth Vol. 352; no. 1; pp. 9 - 15
• Main Authors: Chen, Chun-Hung, Chen, Jyh-Chen, Lu, Chung-Wei, Liu, Che-Ming
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.08.2012; Elsevier
• Subjects: A1. Numerical; A2. Crystal growth; B1. Sapphire; B2. Kyropoulos; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Crystal growth; Crystals; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Furnaces; Growth from melts; zone melting and refining; Heaters; Heating equipment; Materials science; Melts; Methods of crystal growth; physics of crystal growth; Physics; Sapphire; Single crystals; Solid-solid transitions; Specific phase transitions; Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation; A2. Crystal growth; B2. Kyropoulos; A1. Numerical; B1. Sapphire; Crystal growth; Temperature gradients; Digital simulation; Crystallization; Growth interface; Kyropoulos method; Monocrystals; Sapphire; Growth mechanism; Growth from melt; Crystal growth from melts
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2012.01.017

The Kyropoulos (KY) method is commonly used to grow large sized sapphire single crystals. The shape of the sapphire crystal thus grown is determined by the heater arrangement and the power reduction history in the Kyropoulos furnace. In order to grow high-quality sapphire single crystal, the heater arrangement should allow different power inputs in different sections in order to control the thermal field in the melt during the growth process. In this study, a numerical computation is performed to investigate the effects of the heater arrangement on the thermal and flow transport, the shape of the crystal–melt interface, and the power requirements during the Kyropoulos sapphire crystal growth process in a resistance heated furnace. Four different power ratio arrangements in a three-zone heater are considered. The results show that for the power arrangements considered herein, the temperature gradients along the crystallization front do not exceed 0.05K/mm, and that, after the growth of the crown, the crystal maintains an almost constant diameter. The remelting phenomenon may occur during growth when the input power of the upper side of the heater is higher than that of the lower side of the heater. ► The three-zone heater allows different power inputs in different sections. ► The effect of the power arrangement on the transport phenomena is investigated. ► The shape of the sapphire crystal is determined by the power arrangement. ► An optimum power arrangement has been proposed.