Cr3+ chemical diffusivity in aliovalent doped aluminas

Average lattice diffusivities of Cr3+ in undoped, MgO-doped, and SiO2-doped Al2O3 have been measured between 1100 and 1300 °C using scanning transmission electron microscopy based x-ray energy dispersive spectroscopy. It has been demonstrated that both MgO and SiO2 dopants have negligible effect on lattice Cr3+ chemical diffusion. The experimentally determined Arrhenius equations for undoped, MgO-doped, and SiO2-doped samples are Dundoped=1.9×10−10exp(−298kJ/molRT)m2/s, DMgO=2.0×10−13exp(−217kJ/molRT)m2/s, and DSiO2=6.2×10−11exp(−273kJ/molRT)m2/s, respectively. The weak dopant effect is discussed in the context of the contributions from both extrinsic point defect concentrations and their cluster binding energies.