Effect of the pulling rate on the quality of cerium-substituted YIG single-crystal fibers by LHPG

CeO2 was added into yttrium iron garnet materials (YIG). Samples with a nominal composition of Y3−xCexFe5O12 (Ce:YIG), with x=0–0.4, were grown in air by the laser-heated pedestal growth technique. It is well known that it is difficult to grow pure YIG single-crystal fibers, due to the oscillatory instability of the melt and to the incongruent melting of the compound. In this work CeO2 was added during the growth of YIG, which caused the composition and the flow in the melt to change. The growth conditions for producing good-quality Ce:YIG single crystal needs to be suitably adjusted in comparison with YIG growth. In the experimental results, it can be seen that the addition of CeO2 into YIG increases the period of the oscillatory flow in the melt. Moreover, the greater the amount of CeO2 added, slower is the pulling rate needed to grow good-quality single-crystal fibers. When a faster pulling rate is used to grow Ce:YIG material, more significant amount of foreign phases and cellular structures will form in the core region than in the peripheral region of the grown crystal fibers. This is thought to be due to the fact that the solute concentration and the experimental segregation coefficient along the convex shape of the growth interface in the melt were non-uniform.