PURPOSE:To easily and stably obtain single crystal by passing the sintered rod for a raw material through the inside of an infrared convergent band melting furnace at high speed and making the sintered rod uniform and dense and thereafter passing the same through the inside of the furnace at low speed and crystallizing it in the case of using the melting furnace and growing single crystal in a band melting method. CONSTITUTION:MgO and Al2O3 are mixed with oxides of lanthanoid elements at such a ratio that single crystal having composition of LnMgAl11O19 (Ln shows lanthanoid elements of La, Ce, Pr, Nd, Sm, Eu, Gd and solid solution thereof) is obtained. The sintered rod for a raw material is produced by forming this mixture and heat-treating the formed body. Then this sintered rod is melted in an infrared convergent band melting furnace equipped with the halogen lamps 4, a quartz pipe 3 and a rotary ellipsoidal mirror 5 or the like. This melt is once passed through a zone at 30-70mm/h speed and the uniform and dense raw material rod M is produced. Then the obtained raw material rod M is again melted in the furnace. While this melt is brought into contact with a seed crystal S, it is passed through the zone at 1-4mm/h. Single crystal of LnMgAl11O19 is grown by a band melting method.
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