IMPROVED RAMAN EFFECT STUDIES ON BORON-CARBIDE (B4.3C)

With a FT Raman spectrometer highly resolved and reliable Raman spectra of B4.3C were obtained largely refuting previous results of other authors. The symmetry selection rules of IR and Raman active phonons are proved to hold. The most prominent Raman doublet at 270/320 and that at 869/928 cm-1 are due to pentagonal pyramids of the icosahedra symmetrically vibrating relative to the end atoms of the three-atomic chain. The broad band at 1065 cm-1 is attributed to corresponding vibrations of pairs of pentagonal pyramids in adjacent icosahedra. The remaining Raman-active phonons, mainly attributed to intraicosahedral vibrations, are comparably weak. At higher photon energies the luminescence radiation due to electron transitions is essential.