INFLUENCE OF THE ATOMIC RATIO OF BORON TO CARBON ON THE PHONON ENERGIES AND THE ELECTRONIC PROPERTIES OF BORON-CARBIDE

The reflectivity of boron carbide was investigated in the visible and the near infrared range on samples with atomic ratios of boron to carbon in the range 2.39-6.4. The phonon energy shift leads us to conclude that the carbon atoms occupy regular sites in the icosahedra. The electronic transitions and their different energy shifts were obtained by a highly sensitive method of measuring the differential reflectivity. Optical and electrical measurements indicate distinct electronic conditions at an atomic ratio of boron to carbon approximately equal to 4. The values of the thermoelectric power indicate the donor character of the carbon atoms in boron carbide. © 1979.