High Temperature Raman Scattering from Boron Nitride Coatings on Resistively Heated Graphite Substrates

摘要

Raman spectra of the hexagonal phase of boron nitride to temperatures exceeding 2000/degree/C, have been recorded using a pulsed-excitation gated-detection method. Surface temperatures were determined during rapid sample heating from analysis of corrected Stokes/anti-Stokes intensity ratios and from shifts in the resonance frequency of the 1366 cm/sup /minus/1/ E/sub g/ mode. Successive spectra were acquired at time intervals as short as 33 msec corresponding to the pulse repetition frequency of the probe laser. Using this synchronous detection technique, the time evolution of graphite furnace temperature was determined from measured spectra. Results indicate nearly complete rejection of sample blackbody from the Raman scattered light at these high temperatures. A nearly linear relationship between the Eg resonance frequency and temperature was found. Phonon linewidths were also found to increase by a factor of three over this temperature range. 5 refs., 6 figs. (ERA citation 14:015278)