Zirconia single crystal

For instance, dislocations have been shown to play a key role in the accommodation process in YTZP, justifying the threshold stress in YTZP, in contrast with the hypothesis that this threshold stress is due to the electric field created by impurity segregation. However, dislocations are not systematically observed in YTZP furthermore it was shown that in yttria-stabilized tetragonal zirconia single crystals, the stress necessary to activate dislocations at 1400°C was over 400 MPa, one order of magnitude higher than the stresses used during superplastic deformation of YTZP at the same temperature. It will be necessary to conduct a systematic study of the microstructure of the monolithic ceramics such as YTZP before and after deformation and to correlate their relationship with the superplastic features. 

Zhuiykov, S., Zirconia single crystal analyser for low-temperature measurements. Process Control and Quality 11 (1998) 23-37. 

FIGURE 4.5 Sideway view of zirconia single-crystal sensor elements and oxygen probe. 

FIGURE 4.6 S ample of a zirconia single crystal made by an inductive high-frequency melting technique. (From Zhuiykov, S., Zirconia single crystal analyser for low-temperature measurements, Prvc. Control and Quality 11 (1998) 23-37. With permission.)... 

Table 4.2 shows the concentration of chemical impurities in a zirconia single crystal [8]. The concentration of impurities shown here is low and therefore is unlikely to have a significant influence on the ionic conductivity of the zirconia single crystal at low temperatures. The level of impurities concentration shown in Table 4.2 indirectly confirmed that the partial electronic conductivity of the singlecrystal zirconia is negligible. 

Concentration of Chemical Elements as Impurities in Zirconia Single Crystal... 

The emf of the zirconia single-crystal sensor with the Bi-tBijOj RE as a function of measuring temperature at the different oxygen concentrations is shown in Figure... 

It is also essential to know the cross-sensitivity of the zirconia single-crystal sensors to other gases. Sensors with porous Pt electrodes are known to be sensitive to gases such as CO at low temperatures [41], and in fact, this cross-sensitivity has been proposed as a principle for carbon monoxide sensors at low temperatures by some researchers [42, 43]. This effect is attributed to the ability of CO to compete successfully with oxygen for adsorption sites on Pt at temperatures from 500°C to 650°C. It was observed that the zirconia single-crystal sensor with thin-film Pt-Zr02-Y2O3 electrodes is less sensitive to CO than similar polycrystalhne sensors with porous Pt electrodes, but small em/errors still occur at 300-360°C. 

The zirconia single-crystal sensor is used both for periodic variations via short-time dipping into the melts, and for continuous measurement. It is vibration impact proof, needs no precalibration, and can be used for certifying other oxygen impurity control instruments. Small cylinders of the zirconia single crystal, mounted into a ceramic insulating tube, can work at allowable thermal shocks of up to 10°C per second... 

The conclusions concerning the proper design and performance of zirconia single-crystal sensors can be summarized as follows [8] ... 

Sober, J.D. et al.. Low-temperature ionic conductivity of 9.4-mol%-yttria-stabilized zirconia single crystal, J. Am. Ceram. Soc. 72 (1989) 1500-1502. 

U. Messerschmidt, B. Baufeld, and D. Baither, Plastic deformation of cubic zirconia single crystals, Key Eng. Mater. 153-154, 143-182 (1998). 

R., and Alonso, P.J. (1990) Intrinsic electron and hole defects in stabilized zirconia single crystals. Phys. Rev. B. (Condens. Matter), 42 (16), 9782-9789. 

Fig. 2.76 Temperature dependence of flexural strength of partially and fully stabilized zirconia single crystals, polycrystalline PSZ, and hot-pressed Si3N4 (HPSN). PSZ is partially stabilized Zr02 with Y2O3 [24], With kind permission of Wiley and Sons...

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