Solid state NMR of B-11 and C-13 in boron carbide, B12C3 and B-11 enriched B12C3

B-11- and C-13-solid state NMR of boron carbide with different isotope ratios, B4C(B-11/B-10 = 80.42/19.58; natural abundance isotope) and (B4C)-B-11(B-11/B-10 = 99.5/0.5; B-11 enriched sample), has been investigated. The linewidth of the icosahedral B (6h(1) and 6h(2)) in B-11-static NMR signal in (B4C)-B-11 was greater in (B4C)-B-11 than in B4C, which indicates that the B-B dipole-dipole interaction is the main mechanism for the broadening of the B-11-static NMR signal. The quadrupole coupling constant calculated from the signal position of (+/-1/2 <---->+/-3/2) transition was about 0.1 MHz. B-11-MAS spectra revealed the presence of at least two additional B sites (37 ppm and near -60 ppm) besides the icosahedral B sites (-6 ppm).