Chemical Diffusion in Polycrystalline Al ₂ O ₃ as Determined from Electrical Conductivity Measurements

Abstract

By analyzing the changes with time of the electrical conductivity of polycrystalline Al 2 O 3 after the O 2 pressure was changed, a defect diffusion coefficient was obtained which was assigned to the Al or O ion, whichever is the faster‐diffusing species. Both decreased grain size and MgO addition increase the defect diffusion coefficient. The grain‐boundary defect diffusion coefficient for the undoped material was estimated to be: image and that for the MgO‐doped material was image over the range 1100° to 1350°C (δ is the effective thickness of the boundary and s the coefficient of segregation of defects to the boundary region). The mechanism of grain‐boundary diffusion is discussed in terms of defect mobility.