The effect of simultaneous doping with Mn and Ti upon diffusional creep was studied in dense polycrystalline alumina, with grain sizes of 4 to 80µm, at 1175 to 1250C. At a total dopant concentration of 0.32 to 0.37 cation%, diffusional creep rates were considerably enhanced, such that the temperature at which cation mass transport was significant was suppressed by at least 200C, as compared to that in undoped material. Here, Mn-Ti (and Cu-Ti) dopant pairs were far more effective in enhancing creep rates and suppressing sintering temperatures than were the Fe-Ti pair. The enhanced mass transport kinetics were suggested to be caused by significant increases in both the Al lattice and grain-boundary diffusion (table 5). When the Al grain-boundary diffusion was enhanced by increasing the concentration of divalent impurities (Mn2+, Fe2+).

Enhancement of the Diffusional Creep of Polycrystalline Al2O3 by Simultaneous Doping with Manganese and Titanium. Y.Ikuma, R.S.Gordon: Journal of Materials Science, 1982, 17[10], 2961-7