Partially stabilized zirconia

Zirconia, partially stabilized elastic properties, 5 614t hardness compared to metals, 5 627t... 

TABLE 1.16 Properties of Zirconia, Partially Stabilized Zirconia, and Toughened Zirconia... 

The following table contrasts the properties of a typical partially stabilized zirconia (PSZ) body as used in this application with a typical fully stabilized (Y2O3) body. 

Figure 10. Ionic conductivity of jully and partially stabilized zirconia bodies...

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. 

It should be noted that it is possible to produce fully stabilized bodies with much higher fracture strengths than listed here but this requires the use of fine particle size, chemically prepared powders (3). The use of this type of material involves a number of penalties both in cost and processability that may be prohibitive for a high volume automotive application. In addition to the type of partially stabilized body described here, two other basic types of partially stabilized bodies have been reported (4, ). Both are classified as transformation toughened partially stabilized zirconias and involve different processing techniques to obtain a body with various amounts of a metastable tetragonal phase. While the mechanical properties of these materials have been studied extensively, little has been reported about their electrical properties or their stability under the thermal, mechanical and chemical conditions of an automotive exhaust system. 

Figure 13. SEM micrograph of yttria partially stabilized zirconia body (bar = 0.75 micron)...

Oxygen sensors, in low volume use as part of a closed loop emission control system for automotive applications since 1977, have seen wide-spread use starting with the 1981 model year. At the present time, a partially stabilized zirconia electrolyte using yttrium oxide as the stabilizer appears to be the most common choice for this application. 

Hydroxyapatite (HAP), with basically the same crystal structure as Ca-deficient, carbonate-containing hydroxyapatite, is compatible with and reactive in a live human body. However, sintered HAP prepared by treating fine HAP particles under elevated temperature and pressure has insufficient mechanical properties, in particular fracture toughness, which greatly limits its commercial applicability. It is rarely implanted alone. On the other hand, zirconia, particularly partially stabilized zirconia (PSZ),... 

Ceramics (qv) such as those in Table 12 find high temperature use to over 800°C (32). Advanced ceramics finding interest include alumina., partially stabilized zirconia, silicon nitride, boron nitride, silicon carbide, boron carbide, titanium dibofi.de, titanium carbide, and sialon (Si—Al—O—N) (33) (see... 

SYNTHESIS AND CHARACTERIZATION OF POLY (MAGNESIUM ACRYLATE) AND POLY(ZIRCONYL ACRYLATE) TOWARDS THE FORMATION OF MAGNESIUM PARTIALLY STABILIZED ZIRCONIA CERAMICS... 

Mg-PSZ represents magnesia, MgO, partially stabilized zirconia, Zr02, ceramics. These ceramics are strong and tough structural materials. The main characteristics of Mg-PSZ ceramics are... 

As an attempt to solve this problem, zirconia is "stabilized" in the cubic phase by alloying it with an appropriate amount of di-or tri-valent oxide of cubic symmetry such as CaO, MgO or Y203. This results in a lowering of the temperature for the two lowest temperature transitions. These alloys are called partially stabilized zirconia, PSZ and they are a mixture of cubic and monoclinic or tetragonal phases and fully stabilized zirconia (all cubic phase) depending upon the concentration of the "dopant" or added metal oxide. 

Ceramic materials such as partially stabilized zirconia can also be used as die liners. Ceramics offer high wear and corrosion resistance and lower tablet ejection forces than either steel or carbide due to their low coefficient of friction. 

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