Fabrication of novel ZrO₂(Y₂O₃)–Al₂O₃ ceramics having high strength and toughness utilising pulsed electric current pressure sintering (PECPS)

Abstract

Pulsed electric current pressure sintering (PECPS) makes it possible to produce novel monolithic and composite materials with well controlled microstructure or nanostructure, which has not been realised before. ZrO₂ based ceramics containing 25 mol.-%Al₂O₃ and 0·90–1·125 mol.-%Y₂O₃, i.e. ZrO₂(1·2–1·5 mol.-%Y₂O₃)–25 mol.-%Al₂O₃, revealing high bending strength σ_b≧1 GPa and high fracture toughness K_IC ≧15·5 MPa m^1/2 simultaneously, have been fabricated by PECPS of cubic ZrO₂ solid solution (ss) powders containing both Al₂O₃ and Y₂O₃ prepared via a sol–gel process. Tetragonal ZrO₂ (t-ZrO₂) phase composite ceramics sintered at 1573 to 1623 K (1300–1350°C) for 10 min under 60 MPa in Ar were composed of ∼φ200 nm grains with high relative density ≧97·5%. Transmission electron microscopy observation cleared that these mechanical properties might originate from homogeneous distribution of α-Al₂O₃ particles in the dense t-ZrO₂ matrix; the precipitation of α-Al₂O₃ could be achieved by adopting the ss powders and PECPS.

Keywords:

• Zirconium oxide
• Aluminium oxide
• Yttrium oxide
• Solid solution
• Sol–gel process
• Pulsed electric current pressure sintering
• Mechanical properties

Acknowledgements

This work was supported by the ‘Advanced Study for Integrated Particle Science and Technology’, Strategic Development of Research Infrastructure for Private Universities, grant no. S0901039, the Ministry of Education, Culture, Sports, Science and Technology, Japan. In addition, the authors thank Ms M. Toda and Ms J. Morita of Doshisha University Research Interfacial Phenomenon for FE-SEM and FE-TEM observations of the samples.