Yttria stabilized body

CaO has been used to some degree as a stabilizer and is attractive due to its low cost. Its ionic conductivity, however, is approximately an order of magnitude less than an equivalent yttria stabilized body. There has also been some question about the chemical stability of a CaO stabilized body, although this may be more of a factor with a partially stabilized body than a fully stabilized body. Calcia fully stabilized ZrO has been and may still be used in commercial production of oxygen sensors. 

As can be seen, the mechanical strength of the partially stabilized body is approximately twice that of the fully stabilized and the thermal expansion is approximately 30% lower. Because of this, the thermal shock resistance of the PSZ body is greatly improved. The ionic conductivity of the PSZ body is lower but is still adequate for automotive applications. Figure 10 compares the conductivity of a yttria partially stabilized zirconia body with several fully stabilized bodies. 

Figure 10.10 Temperature dependence of sintered density for an agglomerated or as-received and agglomerate-free yttria-stabilized zirconia powder (Ih). Eliminating the agglomerates in the green body resulted in a powder compact that densified much more readily. " ...

It is said that the yttria-stabilized zirconia (Y-TZP) generally used will degrade if it remains for a long period of time under low-temperature and moist conditions, such as in the human body. Indeed, Piconi et al. have reported on a case of fracture of an artificial hip joint made of Y-TZP. 

Bioceramic Applications The performance requirements of yttria-stabilized tetragonal zirconia polycrystal (TZP) to form biocompatible, strong components for use as hip, knee, and dental prostheses, and which demonstrate long-term resistance against aggressive body fluids and mechanical wear and tear, during a predicted lifetime of 15-20 years in the human body, include ... 

Figure 11. Optical micrograph of high silica content (> 1%) yttria fully stabilized zirconia body (bar = 37 microns)...

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