High‐Strength and High‐Fracture‐Toughness Ceramics in the Al2O3/LaAl11O18 Systems

Control of microstructure in the Al 2 O 3 /LaAl 11 O 18 system was performed. Elongated alumina grains were formed by doping with small addition of silica, and 20 vol% lanthana‐ luminate was formed in situ by the reaction of LaAlO 3 ‐ A1 2 O 3 in an alumina matrix. Strengths of over 600 MPa and a high fracture toughness (6 MPa.m 1/2 ) were achieved in the material with both elongated A1 2 O 3 grains and LaAl 11 O 18 platelets. Generally antagonistic properties such as strength and fracture toughness have been made compatible in the same ceramic system.