X-ray line-broadening study of a liquid-phase-sintered silicon carbide

Silicon carbide (SiC), owing to its unique combination of chemical and physical properties, is the material of choice for advanced engineering applications both at room and high temperatures. Due to the difficulty of SiC to be solid-state sintered, nowadays there has been growing interest in liquid-phase sintering (LPS) of SiC. Here, there is a critical need for developing methodologies for the accurate X-ray diffraction characterization of the microstructures of these ceramics as their microstructural evolution is not yet totally understood. Thus, the aim of the present work is to apply a procedure for the accurate line-broadening study of any given phase in LPS SiC ceramics. To that end, we have pressureless liquid-phase sintered (at 1950 °C for 0.5 h in flowing Ar atmosphere) a specimen starting from a commercially available β-SiC powder and using the simultaneous addition of Al2O3 and Y2O3. The resulting material was subsequently characterized using X-ray powder diffraction; more specifically, the Rietveld method was applied for the quantitative phase-composition analysis and the Warren–Averbach method for determining the mean crystallite size, the crystallite size distribution and the root-mean-square strain along the crystallographic direction <111> of the β-SiC polytype. The nanometric nature of the crystallite size distribution is finally related with the stacking faults in the SiC starting powder.