Sintering Kinetics and Microstructure Evolution in α-Al2O3 Nanocrystalline Ceramics: Insensitive to Fe Impurity

Abstract Diffusion kinetics, processing, and microstructures of alumina ceramics have been of great scientific and technological interests. Here we reported the sintering kinetics and microstructure evolution in high-purity dispersed ultrafine α-Al2O3 nanoparticles with superior sinterability. An extremely fine grain size of 34 nm with 99.6% theoretical density and a uniform microstructure can be produced by two-step pressureless sintering. Systematic kinetic analysis further points out to a surprising insensitivity of α-Al2O3 nanocrystalline ceramics to Fe and other impurities, which contrasts with prior reports in the literature. We propose this insensitivity is originated from extensive grain boundaries in nanocrystalline ceramics, which allows segregation of impurities and lowers their concentrations at grain boundaries.