Thermal effects in Raman spectra of hexagonal boron nitride and nanotube-containing boron nitride soot

Abstract

The temperature-induced changes in Raman spectra of two BN-based materials: a hexagonal boron nitride and soot with single-wall BN nanotubes, have been measured in temperature range 77-600 K in course of heating in the oven/cryostat cell. A nonlinear temperature dependence of the tangential Raman mode position (being at 1366 cm-1 at room temperature) has been observed for both materials. In the temperature range 350-600 K a linear approximation of the tangential Raman mode shifting was applicable. The measured rates were -0.014 cm-1/K (for h-BN) and -0.027 cm-1/K (for the nanotube-containing sample). The effects of the oven and laser heating have been compared. Under the laser heating with the same power density the nanotube-containing soot demonstrated much bigger shifts (up to 30cm -1) than h-BN. The data obtained are useful for In-situ diagnostics of different BN-based phases in course of synthesis. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.