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http://dx.doi.org/10.6111/JKCGCT.2019.29.1.024

Melting of Al2O3 powder using the skull melting method  

Choi, Hyun-Min (Hanmi Gemological Institute & Laboratory)
Kim, Young-Chool (Hanmi Gemological Institute & Laboratory)
Seok, Jeong-Won (Advanced Materials & Energy Engineering, Dongshin University)
Publication Information
Journal of the Korean Crystal Growth and Crystal Technology / v.29, no.1, 2019 , pp. 24-31 More about this Journal
Abstract
The current study demonstrates an efficient procedure to create ingots from $Al_2O_3$ powder using the skull melting method to use these ingots as a starting material in conventional methods for growing synthetic single-crystal sapphire. Dimension of the cold crucible was 24 cm in inner diameter and 30 cm in inner height, 15 kg of $Al_2O_3$ powder was completely melted within 1 h at an oscillation frequency of 2.75 MHz, maintained in the molten state for 3 h, and finally air-cooled. The areal density and components of the cooled ingot by parts were analyzed through scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). The areal density and $Al_2O_3$ content of the ingot were related to the temperature distribution inside the cold crucible during high-frequency induction heating, and the area with high temperature was high tends to be high in areal density and purity.
Keywords
Skull melting method; $Al_2O_3$ powder; Cold crucible; Synthetic single-crystal sapphire;
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