Alumina powders with varying iron oxide contents were prepared by coprecipitation. The powders were spheroidized by passing them through an oxygen‐acetylene flame. The spheres were sized, annealed, and sintered in air and in N 2 with 132 ppm O 2 . Isothermal studies were combined with constant‐rate‐of‐heating studies to identify the mechanism of sintering and to calculate the diffusion coefficients. The contribution of surface diffusion during initial‐stage sintering of Fe‐doped Al 2 O 3 was estimated by combining shrinkage and neck‐growth data. The effect of Ti on the sintering rate of Fe‐doped Al 2 O 3 was also studied. Both Fe 2+ and Ti 4+ ions enhanced the sintering rate of Al 2 O 3 . A defect model for corundum is proposed to explain the sintering data for transition‐metal‐ion‐doped Al 2 O 3 .
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Rao et al. (1973) studied this question.
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