VALENCE-BAND ELECTRON-STRUCTURE IN POLYCRYSTALLINE CUBIC BORON-NITRIDE SINTERED IN SHOCK-WAVES

Measurements have been made on the phase composition, valence-band ele ctron-energy structure, the substructure, and the lattice parameters. Internal stresses have been determined in the BN(sp) polycrystalline m aterials sintered in shock waves with various pressures at the fronts. The NK(alpha) spectra show that the valence bands are shifted to ener gies that correspond to points of high symmetry U1 and K1 in the Brill ouin zone. They represent sp hybridized states, which participate in d irect bonds between the closest boron and nitrogen atoms. The reductio n in the electron-state spaces in these energy regions is related to t he internal stresses, which attain some gigapascals. These arise from the formation of point and line defects. The type of defect has a mark ed effect on the internal-stress sign and level.