Design of two-phase inductor circuit for the floating-zone crystal growth

The present work is concerned with the growth of small-diameter single intermetallic compound crystals by the floating-zone method using a radio frequency RF induction heating. In order to maintain a convex solidification interface, which is required for the growth of single crystals, we have developed a novel two-phase inductor comprising a secondary coil, which is short-circuited through capacitor and resistor. The former is adjusted to have resonance in the secondary circuit, which results in a 90 degrees phase lag of the secondary current relative to the primary one. However, it is not always possible to tune the secondary circuit into the resonance as it turns out to be incompatible with the operation of contemporary self-tuning RF-generators. We show that the resonance frequency is unstable unless the resistance of the secondary circuit is made high enough. Analytical results are confirmed by both numerical simulation of the circuit system using the Simulink and measurements on the floating-zone crystal growth facility equipped with a two-phase inductor.