Fabrication of Al2O3/AlN composite ceramics with enhanced performance via a heterogeneous precipitation coating process

To improve the thermal and mechanical properties of Al 2 O 3 /AlN composite ceramics, a novel heterogeneous precipitation coating (HPC) approach was introduced into the fabrication of Al 2 O 3 /AlN ceramics. For this approach, Al 2 O 3 and AlN powders were coated with a layer of amorphous Y 2 O 3 , with the coated Al 2 O 3 and AlN powders found to favor the formation of an interconnected YAG second phase along the grain boundaries. The interconnected YAG phase was designed to act as a diffusion barrier layer to minimize the detrimental interdiffusion between Al 2 O 3 and AlN particles. Compared with samples prepared by a conventional ball-milling method, the HPC Al 2 O 3 /AlN composites exhibited less AlON formation, a higher relative density, a smaller grain size and a more homogeneous microstructure. The thermal conductivity , bending strength , fracture toughness and Weibull modulus of the HPC Al 2 O 3 /AlN composite ceramics were found to reach 34.21 ± 0.34 W m −1  K −1 , 475.61 ± 21.56 MPa, 5.53 ± 0.29 MPa m 1/2 and 25.61, respectively, which are much higher than those for the Al 2 O 3 and Al 2 O 3 /AlN samples prepared by the conventional ball-milling method. These results suggest that HPC is a more effective technique for preparing Al 2 O 3 /AlN composites with enhanced thermal and mechanical properties, and is probably applicable to other composite material systems as well.