Density of feed rod dependence of the PrB${}_6$ single crystal grown by the optical floating zone technique

Rare‐earth hexaboride single crystals praseodymium hexaboride (PrB${}_6$) are successfully grown by the optical floating zone technique using the feed rods with different densities sintered by spark plasma sintering (SPS). Single crystal X‐ray diffraction and transmission electron microscopy analysis have found that the as‐grown PrB${}_6$ adopts a single crystalline structure which has a primitive cubic structure, and has grown along the <100> direction. Particular attentions are given to the effect of density of feed rod on the crystal quality and thermionic emission performance of PrB${}_6$ single crystals. The result of X‐ray rocking curve indicates that the quality of the as‐grown single crystals get better with increase in the density of feed rod, and an ultralow full‐width at half‐maximum of 0.066°, confirming the good crystal integrality, is resulted from the single crystal using the feed rod with relative density of 97.17%. Similarly, the result of thermionic emission shows that the PrB${}_6$ single crystal grown here using a high‐density feed rod has a large current density. The density of feed rod plays an important role in PrB${}_6$ single crystal growth by the optical floating zone technique. (© 2019 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)