Determination of Thermal Properties of Carbon Materials above 2000 °C for Application in High Temperature Crystal Growth

This work reports on the determination of the heat conductivity of high temperature stable carbon materials in the temperature range well above 2000 degrees C where classic material characterization methods fail. Dense graphite (DG) materials as well as rigid and soft felt isolation (RFI/SFI) components have been investigated which are used during crystal growth of SiC by the physical vapor transport method (PVT) in the temperature regime of 2000 and 2400 degrees C. The applied materials characterization methods include low temperature physical heat conductivity measurements using laser flash analysis (LFA) in the temperature range 25-1200 degrees C, data extrapolation to elevated temperatures up to 2400 degrees C, and a correlation of heating processes and computer simulation of the temperature field of different hot zone designs. Using this approach, the calculated temperatures and experimentally determined values with an error of less than +/- 2% at 2400 degrees C can be merged. This work reports on the determination of the heat conductivity of high temperature stable carbon materials in the temperature range well above 2000 degrees C where classic material characterization fails. Using this method, it is possible to merge temperature field simulations and experimentally determined temperatures of a PVT setup for SiC growth with an error of less than +/- 2% at 2400 degrees C. image