Building upon work in which we examined defect production and stability in spinels, we now turn to defect kinetics. Using temperature accelerated dynamics (TAD), we characterize the kinetics of defects in three spinel oxides: magnesium aluminate $\mathrm{Mg}{\mathrm{Al}}_2{\mathrm{O}}_4$, magnesium gallate $\mathrm{Mg}{\mathrm{Ga}}_2{\mathrm{O}}_4$, and magnesium indate $\mathrm{Mg}{\mathrm{In}}_2{\mathrm{O}}_4$. These materials have varying tendencies to disorder on the cation sublattices. In order to understand chemical composition effects, we first examine defect kinetics in perfectly ordered, or normal, spinels, focusing on point defects on each sublattice. We then examine the role that cation disorder has on defect mobility. Using TAD, we find that disorder creates local environments which strongly trap point defects, effectively reducing their mobility. We explore the consequences of this trapping via kinetic Monte Carlo (KMC) simulations on the oxygen vacancy $\left({\mathrm{V}}_{\mathrm{O}}\right)$ in $\mathrm{Mg}{\mathrm{Ga}}_2{\mathrm{O}}_4$, finding that ${\mathrm{V}}_{\mathrm{O}}$ mobility is directly related to the degree of inversion in the system.

• Received 7 November 2006

DOI:https://doi.org/10.1103/PhysRevB.75.104116