Raman spectroscopy of pressure-induced amorphous boron carbide

We report low- and high-temperature Raman spectroscopy of pressure-induced amorphous boron carbide (a-B4C). Coarsening of carbon clusters in a-B4C was characterized during heating, whereas unusual temperature coefficients of a-B4C Raman peak shifts were observed during cooling. These results experimentally evidence that the amorphization of B4C is associated with the destruction of the C-B-C chains and a-B4C is composed of sp(2) carbon aromatic rings and boron clusters. This disordered structure with relatively weak carbon sp(2) bonds is believed to be responsible for the loss of B4C shear strength at high pressures. (c) 2006 American Institute of Physics.