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 degrees-1450 degrees C) in order to close porosity without significant grain growth. The second step at temperatures around 1150 degrees 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 mu m was prepared by two-stage sintering. A standard sintering process resulted in ceramics with identical relative density and a grain size of 1.6 mu m.