Effects of rotating magnetic field on Bi12SiO20 crystal growth by vertical zone-melting technique

Two Bi12SiO20 single crystals ∅10×30 mm2 were grown with and without a rotating magnetic field by the vertical zone-melting technique. Growth striations are completely absent and defects almost could not be found inside the crystal grown with a rotating magnetic field, while striations and numerous defects could be found inside the single crystal grown without a rotating magnetic field. The mechanism of effect of a rotating magnetic field on the growth of Bi12SiO20 crystals is tentatively proposed so that the rotating magnetic field induces a current and consequently generates a forced convection in the melt. If a steady, axisymmetric and desirable convection is generated by the applied rotating magnetic field, the transport of heat and mass in the melt near the crystal–melt interface is enhanced and maintains stability. As a result, the crystallographic perfection and homogeneity of the grown crystal could be significantly improved by using a rotating magnetic field combined with the vertical zone-melting technique.