The effects of microstructure on mechanical and electrical properties of W dispersed Al2O3 ceramics

摘要

This work aims to enhance the fracture toughness of brittle Al2O3 ceramics and apply insulated Al2O3 ceramics with electrical conductivity by dispersing second tungsten (W) metal particles. In order to investigate the effects of W dispersion on mechanical and electrical properties, Al2O3-W composites with various amounts of W (ranging from 5 vol% to 20 vol%) were fabricated by the hot-press sintering method at various sintering temperatures. Microstructure analysis revealed submicron Al2O3 matrix grains and W particles. The existence of three phases of Al2O3, W, and AlWO4 was confirmed by X-ray diffraction patterns. All Al2O3-W composites showed higher fracture toughness than monolithic Al2O3. The toughening mechanism was attributed to crack deflection and crack bridging. Transgranular fracture was visible in all composites. Electrical resistivity dramatically lowered from 2.9 x 10(12) omega cm of monolithic Al2O3 to 4.1 x 10(2) omega cm of the composite with 20 vol% W addition. The percolation threshold is calculated as 18.5%. With the increase in sintering temperature, the amount of W particles was decreased and Al2O3 grains became large, leading to the reduced number of conductive pathways formed by the dispersed W particles. As a result, electrical conductivity was decreased.