Growth of Large Rutile Single Crystal by Heater-Inserted Floating Zone Method

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Rutile single crystals have attracted much attention for their applications as polarizar. The single crystal have success fully grown by the floating zone (FZ) method, which is difficult to grow large size crystals because the molten zone is kept only by surface tension of the melt. In this study, we have grown large rutile single crystals by the heater-inserted floating zone (heater-inserted FZ) method, in which the melts were supported at the bottom of the iridium crucible and growing crystals The size of a hole at the crucible center should be 2mm in diameter to keep continuous feeding of the melt to the growth region. The use of heat insulating materials made of porous zirconia was effective to melt the rutile. A heat-shielding plate below the crucible was also effective to shallow temperature gradient.Continuous feeding of raw materials were possible to grow for long time by using granular TiO_n. Rutile single crystals with about 25mm in diameter were successfully grown by the heater-inserted FZ method. It will be possible to grow rutile single crystals having larger diameters by a larger crucible.