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A study on the growth mechanism of rutile single crystal by skull melting method and conditions of RF generator  

Seok jeong-Won (Department of Gemological Engineering, Dongshin University, Ceramic Processing Research Center(CPRC))
Choi Jong-Koen (Department of Gemological Engineering, Dongshin University, Ceramic Processing Research Center(CPRC))
Publication Information
Journal of the Korean Crystal Growth and Crystal Technology / v.15, no.5, 2005 , pp. 175-181 More about this Journal
Abstract
Ingots of rutile single crystals were grown by the skull melting method, and their characteristics were compared in terms of melt-dwelling time for each melt. The method is based on direct inductive heating of an electrically conducted melt by an alternating RF field, and the heating is performed by absorption of RF energy. $TiO_2$ is an insulator at room temperature but its electric conductivity increases elevated temperature. Therefore, titanium metal ring(outside diameter : 6cm, inside diameter : 4cm, thickness 0.2cm) was embedded into $TiO_2$, powder (anatase phase, CERAC, 3N) for initial RF induction heating. Important factors of the skull melting method are electric resistivity of materials at their melting point, working frequency of RF generator and cold crucible size. In this study, electric resitivity of $TiO_2$, $(10^{-2}\~10^{-1}\;{\Omega}{\cdot}m)$ at its melting point was estimated by compairing the electric resitivities of alumina and zirconia. Inner diameter and height of the cold crucible was 11 and 14cm, respectively, which were determined by considering of the Penetration depth $(0.36\~1.13cm)$ and the frequency of RF generator.
Keywords
Skull melting; Ti metal ring; Rutile single crystal; Penetration depth; Cold crucible;
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