Crystalline microstructure of corundum fillers determined from powder X-ray diffraction patterns

X-ray-diffraction microstructural analysis was performed for corundum powders produced from Bayer aluminium hydroxides in different ways and for high purity corundum powders produced from other raw materials. Crystalline microstructure characterised by prevalent crystallite shape, volume-weighted crystallite size distribution and second-order crystalline lattice strain distribution was determined through modelling crystallite shapes as hexagonal prisms, with the resulting mean volume-weighted standardised crystallite size in the range 406-1941 Å, height-to-base-diagonal ratio in the range 0.68-0.94 and the mean-absolute second-order strain in the range 0.028-0.087%. Crystallite size distributions were found to be well approximated as bimodal logarithmic-normal ones and consequently four types of microstructure were recognized as depending on precursors and methods of production.