Fabrication and mechanical properties of cordierite/ZrO₂ composites by pressureless sintering

Cordierite/ZrO₂ composites with 5 to 25 wt% ZrO₂ were fabricated by pressureless sintering, and their densification behavior, fracture strength, fracture toughness, microstructure and thermal expansion behavior were studied. The ZrO₂ addition into cordierite matrix affects the densification behavior and mechanical properties of the composites. By dispersing 25 wt% ZrO₂, densified cordierite/ZrO₂ composite with a relative density of 98.5% was obtained at optimum sintering condition of 1440°C/ 2H. Both fracture strength and toughness were enhanced with increasing ZrO₂ content. The fracture strength and toughness were increased from 140 to 290 MPa and from 1.6 to 3.5 MPa·m^1/2, respectively, by dispersing 25 wt% ZrO₂ into the cordierite matrix. ZrO₂ particles were homogenously dispersed into cordierite matrix, which intragranular particles were fine (< 100 nm) and intergranular particles were coarse. The toughening mechanisms in the present composites were mainly attributed to martensitic transformation toughening. Then, the addition of ZrO₂ is likely to have little deleterious effect upon thermal expansion coefficient of cordierite.