title: Nanocrystalline, ultra-degradation-resistant zirconia: its grain boundary nanostructure and nanochemistry.
abstract: Y2O3-stabilized tetragonal ZrO2 polycrystal (Y-TZP) has been known to be an excellent structural material with high strength and toughness since the pioneering study by Garvie et al. in 1975. However, Y-TZP is not considered an environmental or biomedical material because it undergoes an inherent tetragonal-to-monoclinic (T → M) phase transformation in humid or aqueous environment, which leads to premature failure, so-called low-temperature degradation (LTD). In this study, we demonstrate for the first time that this fatal shortcoming of Y-TZP can be resolved by controlling the grain boundary nanostructure and chemical composition distribution in Y-TZP. Nanocrystalline Y-TZP doped with Al(3+) and Ge(4+) ions exhibits no LTD for more than 4 years in hot water at 140 °C, whereas 70% of the tetragonal phase in conventional TZP transforms to the monoclinic phase within only 15 h. This innovative Y-TZP can be fabricated by pressureless sintering at 1200 °C; far below the sintering temperature for conventional Y-TZP. The developed TZP ceramics will be useful in numerous environmental-proofing applications, particularly in the biomedical engineering field.
authors.affiliation: Tokyo Research Laboratory, Tosoh Corporation, 2743-1, Hayakawa, Ayase, Kanagawa 252-1123, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Matsui
authors.affiliation: National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan.
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Yoshida
authors.affiliation: 1] Institute of Engineering Innovation, School of Engineering, The University of Tokyo, 2-11-16, Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan [2] Nanostructures Research Laboratory, Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta, Nagoya 456-8587, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Ikuhara
references.citation: Dent Mater. 2008 Mar;24(3):289-98
references.pmid: 17624420
references.citation: Biomaterials. 1999 Jan;20(1):1-25
references.pmid: 9916767