Newly developed cordierite–zircon composites

Abstract

Cordierite-zircon ceramic composites were fabricated by die pressing a commercial cordierite powder with the addition of up to 10 wt-% zircon (ZrSiO₄). Sintering of cordierite was enhanced by the ZrSiO₄ addition through glass phase formation. With ZrSiO₄ additions above 2·5 wt-% no further effect on the mechanical properties of the composites was observed. The maximum flexural strength at 2·5 wt-%ZrSiO₄ addition was 84±7 MPa, about 30% higher than the 67±5 MPa found for pure cordierite. The strength of cordierite at 2·5 wt-%ZrSiO₄ increased with sintering temperature up to 1300°C, owing to the enhanced densification. Above 1300°C, however, the strength was reduced as a result of the formation of large pockets of glassy phase. The average fracture toughness of cordierite was increased from 1·0 to 1·5 MPa m^1/2 with the addition of ZrSiO. This toughening can be attri4 buted to crack deflection around ZrSiO₄ particles rather than to residual compressive stresses imposed on the cordierite owing to thermal expansion mismatch between cordierite and the ZrSiO₄ second phase.