Influence of Al2O3 on Properties of Yttria Stabilized Zirconia-Al2O3 Composites

摘要

Composite structures of yttria (4.5 mol%) stabilized zirconia (YSZ) with added Al2O3 (0.3 to 7.5 wt%) were investigated. Pressed YSZ compacts prepared from submicrometer powders of >99% purity were sintered in the range 1200-1350 C for 0,5 to 24 h. Uniform grain size microstructures (0.2 to 0.4 micrometers) were obtained which showed discrete Al2O3 grains dispersed throughout. X-ray diffraction and Raman spectral analysis indicated a combination of both cubic and tetragonal phases. Measured lattice parameters were observed to vary irregularly with Al2O3 content. DC conductivity was found to increase with added Al2O3 less than 3 wt%. Strength vaules obtained for the composites were in excess of 9 Mpa x the squareroot of M (K sub Ic) and 425 MPa (MOR), significantly higher thatn reported for cubic phase YSZ. The increased strength was attributed to small grain size as well as to crack deflection and arrest mechanisms associated with the dispersed high modulus and lower expansion second phase. The presence of a monoclinic phase was not detected in the samples either before or after fracture, hence the strengthening could not be ascribed to transformation toughening. Keywords: Fracture toughness.