Grain size dependence of fracture toughness for fine grained alumina

The fracture toughness of a series of fully dense polycrystalline alumina samples prepared by electrical field assisted sintering with grain sizes varying from similar to 290 nm to similar to 3.3 mu m was measured using the surface crack in flexure method. Fracture toughness values for different grain sizes were statistically analyzed based on the Weibull distribution. It was found that the fracture toughness in fine grained alumina is independent of grain size. The characteristic fracture toughness calculated from the Weibull distribution is 3.37 MPa m(1/2). (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.