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Yttria-stabilized zirconia (YSZ) is a zirconium-oxide based ceramic, in which the particular crystal structure of zirconium oxide is made stable at room temperature by an addition of yttrium oxide. These oxides are commonly called "zirconia" (ZrO2) and "yttria" (Y2O3), hence the name.

The addition of yttria to pure zirconia replaces some of the Zr4+ ions in the zirconia lattice with Y3+ ions. This produces oxygen vacancies, as three O2- ions replace four O2- ions. It also permits yttrium stabilized zirconia to conduct O2- ions, provided there is sufficient vacancy site mobility, a property that increases with temperature. This ability to conduct O2- ions makes yttria-stabilized zirconia well suited to use in solid oxide fuel cells, which operate at high enough temperatures.

Contents

Applications

YSZ has a number of applications:

  • For its hardness and chemical inertness (e.g., tooth crowns).
  • As a refractory (e.g., in jet engines).
  • As a thermal barrier coating in gas turbines
  • As an electroceramics due to its ion-conducting properties (e.g., to determine oxygen content in exhaust gases, to measure pH in high-temperature water, in fuel cells).
  • Used in the production of a Solid Oxide Fuel Cell.
  • For its hardness and optical properties in monocrystal form (see "cubic zirconia"), it is used as jewelry.
  • As a material for non-metallic knife blades, produced by Boker and Kyocera companies.
  • In water-based pastes for do-it-yourself ceramics and cements. These contain microscopic YSZ milled fibers or sub-micrometer particles, often with potassium silicate and zirconium acetate binders (at mildly acidic pH). The cementation occurs on removal of water. The resulting ceramic material is suitable for very high temperature applications.
  • YSZ doped with rare-earth materials can act as a thermographic phosphor and a luminescent material.[1]

Related materials include calcia-, magnesia-, ceria- or alumina-stabilized zirconias, or partially-stablized zirconias (PSZ). Stabilized hafnia is also known.

See also

References

  1. ^ J. P. Feist and A. L. Heyes (2000). "Europium-doped yttria-stabilized zirconia for high-temperature phosphor thermometry". Proceedings of the Institution of Mechanical Engineers 214, Part L: 7-11.  

Further Reading

  • Green, D.J.; Hannink, R.; Swain, M.V. (1989). Transformation Toughening of Ceramics. Boca Raton: CRC Press. ISBN 0-8493-6594-5.  
  • X. Chen, Z. Mutasim, J. Price, J. P. Feist, A. L. Heyes and S. Seefeldt (2005), 'Industrial sensor TBCs: Studies on temperature detection and durability', International Journal of Applied Ceramic Technology, Vol. 2, No. 5, pp. 414-421.
  • J. P. Feist, A. L. Heyes and J. R. Nicholls (2001), 'Phosphor thermometry in an electron beam physical vapour deposition produced thermal barrier coating doped with dysprosium', Proceedings of Institution of Mechanical Engineers, Vol. 215 Part G, pp. 333-340.
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