Raman scattering from boron nitride coatings at high temperatures

The temperature dependence from ambient to 2325 K of the high frequency E2g mode intrinsic to the hexagonal phase of boron nitride has been determined using a pulsed-excitation gated-detection technique which effectively discriminates against sample blackbody emission. A monotonic decrease of 80 cm−1 in mode frequency accompanied by a marked increase in linewidth was observed over this temperature range. Simultaneous acquisition of both Stokes and anti-Stokes Raman scattering has been demonstrated and provides another method by which sample temperatures may be verified. Variations in measured linewidth and mode frequency are described in terms of an anharmonic oscillator model from which the intralamellar thermal expansion coefficient is estimated.