AUTOMATIC CRYSTAL-GROWTH OF REFRACTORY-METALS (MO, TA, W) BY THE FLOAT ZONE TECHNIQUE

Single crystals of refractory metals, Mo, Ta and W, were prepared by an automated RF heated floating zone technique. In this method, a computer detected a zone shape from a mutual impedance between the work coil and the molten zone, and controlled the heating power and the feed rate. The molten zone could be passed more smoothly, compared with manual processes. Crystals 6 cm long and 1 cm in diameter were prepared using a 3 h zone pass with automatic control. The automatic growth program was prepared so that it can be applied to the growth of other refractory crystals.