Zirconia tetragonal

Y-TZP = yttria-stabilized tetragonal zirconia polycrystal. LAS = lithium alurninosiUcate. 

Jiang SP and Badwal SPS. Hydrogen oxidation at the nickel and platinum electrodes on yttria-tetragonal zirconia electrolyte. J Electrochem Soc 1997 144 3777-3784. 

Tetragonal structure, of ferroelectric crystals, 11 95, 96 Tetragonal symmetry, 8 114t Tetragonal zirconia polycrystals, 5 571 Tetrahedral... 

Tetragonal zirconia was partly transformed into the cubic phase during the sintering process of the UAP (uniaxially pressed) and CIP-prepared green compacts, and was accompanied by the formation of a-TPC. The transformation tends to accelerate as the PSZ quantity increases. 

On heating to 1500 °C/6 h/Ar, the Zr material crystallizes to a mixture of monoclinic and tetragonal zirconia and crystobalite with loss of considerable original surface area (36 m2 g 1). The Hf material behaves similarly, although it partially crystallizes at 1000 °C to produce cubic or tetragonal hafnia. Cristobalite is only observed in materials heated to 1400 °C. Finally, thin films of the Zr and Hf derivatives could be cast from hydrocarbon solutions on quartz and then converted to thin films of the corresponding amorphous or ceramic materials. 

Nawa, M., Yamazaki, K., Sekino, T. et al, A new type of nanocomposite in tetragonal zirconia polycrystal-molybdenum system, Mater. Lett., 1994, 20(5-6) 299. 

The first observation of superplasticity in a 3 mol% yttria-stabilized tetragonal zirconia polycrystal ceramic (YTZP) with a grain size of 0.4 pm was reported by Wakai et al in 1986 (Fig. 16.1). Since then, a large number... 

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. 

Berbon, M.Z., and Langdon, T.G., An examination of the flow process in superplastic yttria-stabilized tetragonal zirconia , Acta Mater, 1999, 47, 2485-95. 

Morita, K., and Hiraga, K., Critical assessment of high-temperature deformation and deformed microstructure in high-purity tetragonal zirconia containing 3 mol% yttria , Acta. Mater., 2002, 50, 1075-85. 

Mimurada, J., Nakano, M., Sasaki, K., Ykuhara, Y., and Sakuma, T., Effect of cation doping on the superplastic flow in yttria-stabilized tetragonal zirconia poly crystals , J. Am. Ceram. Soc, 2001, 84, 1817-21. 

Sato, E., Morioka, H., Kuribayashi, K., and Sundararaman, D., Effect of small amount of alumina doping on superplastic behaviour of tetragonal zirconia , J. Mater. Sci., 1999, 34, 4511-18. 

Gomez-Garcia, D., Lorenzo-Martin, C., Munoz, A., and Dommguez-Rodriguez, A., Model of high-temperature plastic deformation of nanocrystalline materials Application to yttria tetragonal zirconia , Phys. Rev., 2003, B67, 144101-1-8. 

Transformation of tetragonal zirconia phase to monoclinic phase has been studied in [53], Calcination of zirconium hydroxide ZrO(OH)2 at various temperatures produced three types of paramagnetic centers assigned to trapped electrons located in oxygen vacancies of Zr02 (g = 2.0018), to adsorbed 02"... 

Tokiy N., Konstantinova T., Savina D., Tokiy V. (2003) Computational modeling of electron properties of 26 d-elements in nanolayer Y-doped tetragonal zirconia. Computational Modeling and Simulation of Materials II, Advances in Science and Technology, 36, P.Vincenzini,A.Lami(Eds),Techna Sri, p. 121-128. 

Use the following values of the elastic-stiffness constants and the elastic-comphance constants (Kisi and Howard, 1998) for tetragonal zirconia monocrystals to determine the Voigt-Reuss-HiU averages for the Young s modulus, E, the shear modulus, G, and the bulk modulus, B. 

FIGURE 13M Cake thickness versus casting time for sdttria stabilized tetragonal zirconia suspension. Data taken from Moreno et al. [18]. 

IR spectra clearly distinguish the three zirconia polymorphs [57]. The high-temperature cubic phase has only one IR active skeletal mode, found near 550 cm for powders, while tetragonal zirconia (the medium-temperature polymorph) has... 

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