Yttria-stabilized Zirconia - Stabilization

Stabilization

Pure zirconium dioxide undergoes a phase transformations from monoclinic (stable at the room temperature) to tetragonal (at about 1000 °C) and then to cubic (at about 2370 °C). Obtaining stable sintered zirconia ceramic products is difficult because of the large volume change accompanying the transition from tetragonal to monoclinic (about 9%). Stabilization of the tetragonal polymorph of zirconia over wider range of temperatures is accomplished by substitution of some of the Zr4+ ions (ionic radius of 0.82 Å, too small for ideal lattice of fluorite characteristic for the tetragonal zirconia) in the crystal lattice with slightly larger ions, e.g., those of Y3+ (ionic radius of 0.96 Å). The resulting doped zirconia materials are termed stablized zirconias.

Materials related to YSZ include calcia-, magnesia-, ceria- or alumina-stabilized zirconias, or partially stabilized zirconias (PSZ). Stabilized hafnia is also known.