Control and Theoretical Modeling of the Growth Process of AlN Six-fold and Multifold Armed Dendritic Crystals

Through a combinatorial approach involving theory and experiments, this study investigated the mechanism of the dendritic growth of AlN microcrystals during the combustion of Al + 0.1AlF₃ + kAl₂O₃ powder mixtures under nitrogen-rich conditions. The experimentally observed morphology of the dendritic AlN crystals is characterized by the six-fold branches that developed outward within an equatorial plane and secondary dendrites that grew above and below the equatorial plane. The physical mechanisms that lead to the shape-controlled synthesis of AlN dendritic crystals were studied through experimental analysis and theoretical investigation including density functional theory (DFT) calculation and phase-field (PF) crystal growth modeling. Based on the DFT-calculated surface energy values, an energy minimization argument was used to construct the AlN nucleus. PF crystal growth modeling provides the details of the sequential crystallization process of the dendritic AlN crystals. The results of this study provide a complete understanding of the shape-controlled growth of AlN crystals, which aids the rational growth design of AlN and other relevant compounds.