Fabrication of High-Strength & -Fracture Toughness ZrO2/25mol%Al2O3 Composite Ceramics Using High-Pressure (1GPa) Sintering
Ken HIROTA, Hideyuki SATO, Katsuya TAKAOKA, Masaki KATO and Hideki TAGUCHI
Abstract:ZrO2 ceramics containing 25 mol%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 ` 950C for 10 to 60 min under 1 GPa. Dense t-ZrO2(ss)/Al2O3 composite ceramics with a small amount of monoclinic ZrO2 (m-ZrO2) sintered at 900C for 30 min using the calcined powder prepared at 1000C for 1 h in air were composed of around 55 nm grains with a high relative density of 99.9%. They showed extreme high bending strength (b: 1125 MPa) and high fracture toughness (KIC: 15.8 MPaEm1/2) 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 -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 AlO and high-pressure sintering at low temperatures. Key Words:Zirconia solid solution ceramics, Alumina, High-pressure sintering, Mechanical properties, Nanometer-size grains