Two‐Stage Sintering of Alumina with Submicrometer Grain Size

This work verifies the applicability of two‐stage sintering as a means of suppressing the final stage grain growth of submicrometer alumina. The first heating step should be short at a relatively high‐temperature (1400°–1450°C) in order to close porosity without significant grain growth. The second step at temperatures around 1150°C facilitates further densification with limited grain growth. Fine‐grained alumina with a relative density of 98.8% and a grain size of 0.9 μm was prepared by two‐stage sintering. A standard sintering process resulted in ceramics with identical relative density and a grain size of 1.6 μm.