2012 Volume 61 Issue 5 Pages 419-425
ZrO2 ceramics containing 25mol% Al2O3 have been fabricated by sintering cubic or tetragonal ZrO2 (t-ZrO2) solid solution (ss) nanoparticles prepared via a sol-gel process with a piston-cylinder type high-pressure apparatus at 850~950°C for 10 to 60min under 1GPa. Dense t-ZrO2(ss)/Al2O3 composite ceramics with a small amount of monoclinic ZrO2 (m-ZrO2) sintered at 900°C for 30min using the calcined powder prepared at 1000°C for 1 h in air were composed of around 55nm grains with a high relative density of 99.9%. They showed extreme high bending strength (σb : 1125MPa) and high fracture toughness (KIC : 15.8MPa·m1/2) simultaneously. Their mechanical properties were investigated from viewpoints of the microstructure of ceramics by high-resolution TEM observation and XRD analysis. It was clear that high mechanical properties were much related with high relative density, high ratio of t-ZrO2 phase to m-ZrO2, homogeneous distribution of α-Al2O3 particles in the nanometer-size grain matrix of t-ZrO2 ; these might be achieved by adopting both the the sol-gel technique for preparation of solid solution powders containing Al2O3 and high-pressure sintering at low temperatures.
