Newly developed cordierite-zircon composites

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 1300degreesC, owing to the enhanced densification. Above 1300degreesC, 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 ZrSiO4. This toughening can be attributed 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.