The effects of microstructure on mechanical and electrical properties of W dispersed Al 2 O 3 ceramics

Abstract This work aims to enhance the fracture toughness of brittle Al 2 O 3 ceramics and apply insulated Al 2 O 3 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, Al 2 O 3 –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 Al 2 O 3 matrix grains and W particles. The existence of three phases of Al 2 O 3 , W, and AlWO 4 was confirmed by X‐ray diffraction patterns. All Al 2 O 3 –W composites showed higher fracture toughness than monolithic Al 2 O 3 . 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 × 10 12 Ω cm of monolithic Al 2 O 3 to 4.1 × 10 2 Ω 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 Al 2 O 3 grains became large, leading to the reduced number of conductive pathways formed by the dispersed W particles. As a result, electrical conductivity was decreased.