Floating zone growth and high-temperature hardness of YB 4 and YB 6 single crystals

High-quality YB ₄ single crystals were prepared by controlling the composition of the atomic ratio, B/Y, of the molten zone to be 7-8. The preferential growth direction was almost normal to the (1 1 2) plane of the tetragonal crystal lattice, which had the lowest Vickers hardness. YB ₆ crystals epitaxially grew on the YB ₄ crystals. The growth rates of YB ₄ and YB ₆ crystals were inversely proportional to the difference in the composition between the crystal and the molten zone.