Molecular dynamics simulation on Al2O3 grain boundaries with Mg, Ca and Si segregation

Molecular dynamics (MD) simulations were employed to study the properties of Al2O3 grain boundaries (near Sigma 11 tilt) in presence of Mg, Ca and Si dopants. Three initial configuration of boundaries were considered. The excess energies and excess volumes strongly depend on the initial configuration. In addition, the Mg-doped grain boundaries showed a relatively lower distortion and more stable structures, with a tendency toward decreasing excess energy and excess volume, or compared to pure boundaries or those doped with different ions. The diffusion coefficients of each atom type at grain boundary increased in the order Mg>Al>Si>Ca>O. The coordination numbers of atoms at grain boundary were found to be 5 for Al, 4 for Si, 5 for Mg and more than 6 for Ca, against the value of 6 for Al in the bulk. The MD simulation of Mg doped grain boundaries is discussed in terms of the effect of Mg segregation on the grain growth of Al2O3.