Crystallite size reduction of Cr doped Al2O3 materials via optimized high-energy ball milling method

Abstract

α-Al2O3 based compounds have large crystals and it is very difficult to reduce the crystallite size because they are very stable and hard. One way of reducing the crystallite size of the materials is by using high-energy ball milling method. Pure and single-phase micron-sized α-Al2−xCrxO3 (x = 0.1, 0.2, 0.3) materials were successfully obtained via self-propagating combustion method. These materials were then subjected to a simple milling process from their microcrystalline powders. Comparisons between the micron-sized and milled samples in terms of their phase, structure, morphology and crystallite size were discussed. The XRD results reveal that all the milled samples were pure with no impurity or other phases present. Structural parameters are extracted via the Rietveld method, revealing that the cell constant, a, of the milled samples is higher than that of the micron-sized materials by 0.09 % to 0.11 %, resulting in a 0.28 % to 0.39 % increase in cell volume. FESEM results show a gradual decrease in crystallite size with increased milling time. Notably, the method successfully reduces the crystallite size without changing the phase of the materials and preserving the stoichiometry of the Al2−xCrxO3 materials which may offer improved properties in various applications.