IR SPECTROSCOPY CHARACTERIZATION OF VARIOUS TYPES OF STRUCTURAL IRREGULARITIES IN PYROLYTIC BORON-NITRIDE

Samples of pyrolytic BN ceramics were produced by CVD from BCl3-NH3-N2 mixtures at temperatures of 1300-2100-degrees-C, pressures 1-20 torr and varying partial pressures of the components. A theoretical analysi s of the dependences of i.r. spectral band frequencies on interlayer d istance and crystal block size is given. Five BN structure modificatio ns have been found in BN ceramics from i.r. band shape analysis: hexag onal graphite-like, partially ordered, turbostratic, dense amorphous a nd highly dispersed amorphous, whose relative content strongly depends on the synthesis conditions.