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

Abstract To improve the thermal and mechanical properties of Al2O3/AlN composite ceramics, a novel heterogeneous precipitation coating (HPC) approach was introduced into the fabrication of Al2O3/AlN ceramics. For this approach, Al2O3 and AlN powders were coated with a layer of amorphous Y2O3, with the coated Al2O3 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 Al2O3 and AlN particles. Compared with samples prepared by a conventional ball-milling method, the HPC Al2O3/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 Al2O3/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 m1/2 and 25.61, respectively, which are much higher than those for the Al2O3 and Al2O3/AlN samples prepared by the conventional ball-milling method. These results suggest that HPC is a more effective technique for preparing Al2O3/AlN composites with enhanced thermal and mechanical properties, and is probably applicable to other composite material systems as well.