Some properties of single-crystal boron carbide

Large and high-quality floating zone grown single crystals of boron carbide of the composition Bsimilar to4.3C corresponding to the carbon-rich limit B4.3C of the homogeneity range, were presented by Leithe-Jasper and Tanaka at the ISBB'99 in Dinard for the first time. Such crystals now allow determining the physical properties of this refractory semiconductor free from the influence of impurities or coarse structural imperfections. Some solid-state properties of these single crystals like electronic transport properties, IR optical absorption spectrum, IR reflectivity spectrum, FT-Raman spectrum, and Knoop hardness are presented and discussed with respect to the properties of less perfect boron carbide previously determined. Outstanding properties are the hardness exceeding that of technical boron carbide by 14% (parallel toc) and 24% (perpendicular toc) respectively, and the high optical absorption at energies below the absorption edge and the reflectivity strongly increasing towards low frequencies suggesting a destinctly higher contribution of free carriers. (C) 2003 Elsevier Inc. All rights reserved.