The micro-Vickers hardness of LaB6, La0.7Ce0.3B6, La0.82Pr0.18B6 and La0.85Nd0.15B6 crystals was measured from room temperature to 1300C. The rare-earth substituted LaB6 crystals were confirmed to be boundary-free as a result of solid-solution hardening. In addition, hardness measurements revealed that boundary-free LaB6 crystals could be prepared when the growth temperature was decreased to 200C below the melting point, which agreed well with the experimental results found for the traveling solvent floating zone method.

Crystal Quality and High Temperature Hardness of LaB6 Crystals Prepared by the Floating Zone Method. Otani, S., Tanaka, T., Ishizawa, Y.: Journal of Alloys and Compounds, 1993, 202[1-2], L25-8

Figure 2

Hardness as a Function of Temperature