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The measurements of hardness and elastic modulus have been conducted on the (0001) and (101̄1) faces of B4.3C single crystals using nanoindentation. The results are in good agreement with the corresponding values obtained using a conventional microhardness technique on polycrystalline ceramics. Raman microspectroscopy analysis of the nanoindentations shows the appearance of several bands which suggest dramatic structural changes in the indented material. Localized contact loading may lead to damage in boron carbide resulting in disorder or a pressure-induced solid state phase transformation in the region under the indenter, although the exact mechanism responsible for the observed Raman spectra could not be identified at this time. This may explain why little variation in mechanical properties was observed with respect to the crystallographic orientation.

We present Raman spectra of numerous icosahedral boron-rich solids having the structure of α-rhombohedral, β-rhombohedral, α-tetragonal, β-tetragonal, YB 66 , orthorhombic or amorphous boron. The spectra were newly measured and, in some cases, compared with reported data and discussed. We emphasize the importance of a high signal-to-noise ratio in the Raman spectra for detecting weak effects evoked by the modification of compounds, accommodation of interstitial atoms and other structural defects. Vibrations of the icosahedra, occurring in all the spectra, are interpreted using the description of modes in α-rhombohedral boron by Beckel et al. The Raman spectrum of boron carbide is largely clarified. Relative intra-and inter-icosahedral bonding forces are estimated for the different structural groups and for vanadium-doped β-rhombohedral boron. The validity of Badger's rule is demonstrated for the force constants of inter-icosahedral B-B bonds, whereas the agreement is less satisfactory for the intra-icosahedral B-B bonds.

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In this study, the elastic constants of a titanium diboride (TiB2) single crystal were measured using resonant ultrasound spectroscopy. In contrast to previous work, the current results are consistent with the measured elastic constants of TiB2 polycrystals. In addition, the crystal anisotropy of TiB2 was examined. The current data show that the elastic properties of TiB2 are much more isotropic than previously considered.

Specific heat and transport properties are measured on good single crystals of SmB6. The specific heat experiment indicates that there is a gap of near 100 K in the 4f system leaving a very small T linear term. Conductivity experiment indicates that the usual hopping type conductivity changes to a constant value without activation which is, however, three orders of magnitude smaller than the so far believed minimum metallic conductivity. The usual Anderson localization proposed before by us is clearly not applicable. Here, we propose a model of a new type of the Wigner lattice formation. Various anomalous properties mentioned above are explained within this model

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