In-situ growth of needlelike LaAl11O18 for reinforcement of alumina composites

In situ growth of needlelike LaAl11O18 grains reinforcing Al2O3 composites can be fabricated by a coprecipitation method using La(NO3)3radical dot6H2O and Al(NO3)3radical dot9H2O as starting materials. The new two-step process involved firstly preparing needlelike LaAl11O18 grains distributed homogeneously in Al2O3 powder and then pressureless sintering the composite powders. The Al2O3/25 vol.%LaAl11O18 samples pressureless sintered at 1550°C for 4 h achieve relative density up to 96.5% and exhibit a bending strength of 420±30 MPa and a fracture toughness of 4.3±0.4 MPa m1/2.