Zirconia orthorhombic

Ohtaka O, Yamanaka T, Kume S, Ito E, Navrotsky A (1991) Stability of monoclinic and orthorhombic zirconia Studies by high-pressure equilibria and calorimetiy. J Am Ceram Soc 74 505-509 Parker A, Rae JE (1998) Environmental Interactions of Clays. Clays and the Enviromnent. Springer, New York, 271 p... 

Zirconia also undergoes high pressure phase transitions from the monoclinic to two orthorhombic structures. A thermochemical study of these phases, combined with phase equilibrium observations (Ohtaka et al. 1991) suggests that surface energy changes the apparent position of phase boundaries, as well as enhances the kinetics of transformation. However Ohtaka et al. (1991) were unable to quantify these effects. 

For the monoclinic and tetragonal structures, the bulk modulus hovers around 150-200 GPa. Cubic zirconia has higher bulk modulus somewhere around 171-288 GPa. The high-pressure phases have values around 224-273 GPa and 254-444GPa, for the orthorhombic-I and orthorhombic-II phases, respectively. 

Zirconia is known to exist as three, well-defined polymorphs, namely monoclinic, tetragonal, and cubic [173], although the existence of a high-pressure orthorhombic form has also been reported [174]. The lattice parameters of zirconia polymorphs are... 

Orthorhombic zirconia, which is also known as a high-pressure polymorph, appears in Mg-PSZ when it is cooled to cryogenic temperatures [174]. In the nitrogen-quenched 9.4Mg-PSZ sample, the ortho phase is in the majority, at 46.6 ... 

One of the most useful zirconium-based materials is zirconia, Zr02-Zirconia may be found in a variety of phases (i.e., cubic, orthorhombic), exhibits exceptional resistance to fracturing, and is highly chemically inert. Zirconia is an excellent refractory material and has found many applications in high-heat environments. The hardness and high chemical stability of zirconia make this material well suited for dental applications [1,2]. Ceramic biomaterials based on zirconia have gained popularity in a variety of appHcations [3], such as knee and hip replacements, and are noted for their durability [4]. Cubic zirconia is also used in jewelry. 

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