Interdiffusion in the MgO-Al₂O₃ spinel with or without some dopants

With a view to seek an improved understanding of the DIMOX process, interdiffusion of polycrystalline MgO and Al₂O₃ in the temperature range 1473 to 1873 K. was studied by diffusion couple experiments. The interdiffusivities in the spinel layer were calculated as functions of composition and temperature. The spinel portion of the phase diagram in the system MgO-Al₂O₃ was determined from carefully measured compositions at the phase boundaries, and the low temperature spinel region of the phase diagram was confirmed from the present results. For Zn²⁺ as dopant in alumina, the growth rate of spinel thickness seems to increase when compared with that of the diffusion couples without dopant. The samples containing Si⁴⁺ as dopant reveal the formation of a glass phase, and the effect of Si⁴⁺ on the diffusion process appears to be negligible.