Microstructural characterization of ball-milled α-Al₂O₃: bimodal size distribution and shape anisotropy

α-Al₂O₃ prepared by combustion technique was ball-milled in a planetary ball-mill for several hours. A detail microstructural characterization of the ball-milled samples was performed by X-ray line broadening analysis. X-ray diffraction patterns from the milled materials showed super-Lorentzian peak shapes for the α-Al₂O₃ peak profiles, attributed to a bimodal size distribution of the α-Al₂O₃ crystallites, one type of crystallites having spherical and the other having cylindrical morphology. Rietveld analysis using two different phase fractions of α-Al₂O₃ with different microstructural features yielded a low goodness-of-fit of the X-ray data, indicating the suitability of the assumed model.