Floating zone growth and high-temperature hardness of CrB2 single crystals

Single crystals of CrB₂ were prepared by the floating zone method. The crystal quality was improved by controlling the molten zone composition. The crystals preferentially grew normal to the plane which has the lowest Vickers hardness, similar to the other refractory boride crystals. On the growth plane, the direction of the a-plane, which longitudinally exists along the crystal rod, was controlled without the seed crystal by the position of the lower sintered rod. The anisotropy in the hardness was also consistent with morphology of the crystals prepared by the flux growth. In addition, the hardness measurement was useful for estimating the quality of refractory crystals in the floating zone growth.