Zirconia ceramics is second to the alumina ceramics in advanced ceramics application. Their following properties make this material as an important engineering material.
- Very high melting temperature
- Very low thermal conductivity
- Very high strength
- Excellent Chemical inertness
- Very high hardness
- Very high toughness
- Very high refractive index
Zirconium oxide exists in three polymorphic forms:
1) Monoclinic
2) Tetragonal
3) Cubic
The monoclinic form is the only most stable phase at room temperature. During heating the monoclinic phase is transformed to tetragonal at about 1170.C and the tetragonal phase if transformed to cubic phase at about 2370.C. On cooling through the transition temperature tetragonal to monoclinic transformation is occurring associated with a considerable volume expansion of 3 to 5 percent and a shear strain of 1 to 7% which causes catastrophic failure and due to this fabrication of large pure zirconia ceramics becomes impossible.
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