Yttria-doped zirconia

S. Seimanides, P. Tsiakaras, X.E. Verykios, and C.G. Vayenas, Oxidative Coupling of Methane over Yttria-doped Zirconia Solid Electrolyte, Appl. Catal. 68, 41-53 (1991). 

Oxygen reduction on yttria-doped zirconia (YSZ) was first accomplished over 100 years ago (for the purpose of generating light) using a porous platinum electrode. Since then, oxygen reduction on Pt has been one of the most well-studied electrode reaction... 

SOFCs employ a ceramic oxide (ceria- or yttria-doped zirconia, electrolyte... 

Oxygen anions travel from the source side through the solid electrolyte to the sink side (anode) under the combination of the influence of an applied dc electric field and an oxygen chemical potential gradient. At the sink side (the anode of the SOFC), the oxygen anions react electrochemically with both zirconium and yttrium reactants from the sink vapor phase to form the desired product, yttria doped zirconia, and release electrons to the metallic anode. Electrons travel through the external electrical circuit back to the source side for further cathodic reaction. 

Eigure 31 shows a schematic diagram of a lab-made PEVD reactor for depositing yttria-doped zirconia. The sample tube was placed at the center of a large fully dense alumina reactor tube in an electric furnace. Thus, the sample tube separated the reactor tube into two chambers the air chamber inside the sample tube and the chloride chamber between the sample and reactor tubes. Both chambers were evacuated separately. 

Based on the preceding microstructural analysis results, it is clear that PEVD is capable of depositing a tbin layer of yttria-doped zirconia to form a composite anode. This phase is not only in intimate contact with both the solid electrolyte and metallic electrode, but also covers... 

The goal of using solid-state electrolytic reactors is not only to generate electrical power, but also to combine this with an industrially important catalytic reaction, such as dissociation of oxygen-containing compounds like NO [40,41], quantitative oxidation of NH3 to NO [42-44], oxidation of SO2 [45], and methanol [46], ethylene epoxidation [46], or Fischer-Tropsch synthesis [47]. The cross-flow reactor used in this type of study (Fig. 10) [48,49] has a solid electrolyte consisting of yttria-doped zirconia. The plates are electrically connected in series, with a varying number of plates in parallel. The oxidant flow channels... 

Kilo, M., Taylor, M.A., Argirusis, C., Borchardt, G., Lesage, B., Weber, S., Scherrer, S., Scherrer, H., Schroeder, M., Martin, M. Cation self-diffusion of Ca-44, Y-88, and Zr-96 in single-crystalline calcia- and yttria-doped zirconia. J. Appl. Phys. 2003, 94, 7547-52. 

In general, covalently bonded materials are difficult to sinter because of their inherently low value of self-diffusivity. However, using microwave heating, silicon nitride with 20 wt.% yttria-doped zirconia has been sintered at 1400°C in a nitrogen atmosphere at a pressure 0.1 MPa. In contrast, via a conventionally heated hot isostatic press, a sintering temperature of 1850°C and a nitrogen pressure of about 180 MPa were required to densify the same silicon nitride/zirconia composition as completely as was achieved by microwave heating at 1400°C. ... 

Doped materials, where a structural component of the material becomes partially substituted by a dopant species or when external species ingress in the original material as an interstitial ion. The term doping is thus applied to, for instance, yttria-doped zirconias used for potentiometric determination of O2 but also to describe the incorporation of Li in polymers and nanostructured carbons. 

BET areas treatments. and XRD patterns for pure zirconia and yttria-doped zirconia versus heat... 

D. Huang, K.R. Venkatachari, and G.C. Stangle, Influence of yttria content on the preparation of nanocrystalline yttria-doped zirconia, J. Mater. Res. 10(3), 762-773 (1995). 

A. Suresh, M.J. Mayo, W.D. Porter, and CJ. Rawn, Crystallite and grain-size-dependent phase transformations in yttria-doped zirconia, J. Am. Ceram. Soc. 86(2), 360-362 (2003). 

For example, continuous multilayered ZSM-5 films were grown on cordierite modules.[59] Similar films were generated on as-prepared and acid-treated honeycomb substrates.[60] The latter treatments led to silica-rich surface layers their composition affected the Si/Al ratios of the zeolites crystallized on the cordierite. Thin, defect-free Mid-type films were also made on porous alpha-alumina and yttria-doped zirconia substrates using tclrapropylammonium hydroxide (TPAOH) as a structure-directing agent.[61]... 

TjxOi- The Kroger-Vink diagram for yttria-doped zirconia is shown in Fig. 7.16a, the construction of which is left as an exercise to the reader. In pure zirconia, the concentration of oxygen vacancies is simply y/Ks-However, as noted earlier, that value can be dramatically increased by doping with aliovalent cations such as Ca or. Based on this diagram. 

Actual data for yttria-doped zirconia are shown in Fig. 7A6b as a function of temperature, and generally confirm the results shown in Fig. 7.16a. At 1000°C and 10 atm pressure, /jon 10 10 ) 1.0,... 

Yttria-doped zirconia and gadolinia-doped ceria oxygen ion conductors and strontium yttrium zirconium oxide proton conductors are being investigated as the solid electrolyte. 

C. Bemay, A. Ringuede, P. Colomban, D. Lincot, M. Cassir, Yttria-doped zirconia thin films deposited by atomic layer deposition ALD a structural, morphological and electrical characterisation. Journal of Physics and Chemistiy of Solids, 2003, v. 64, N 9-10, p. 1761-1770. 

It can be seen from the figure that, over the temperature range from 1000°C to 400 C, the last two electrolytes have a markedly higher conductivity, than yttria-doped zirconia. It can also be seen from the figure that scandia-doped zirconia has a markedly higher conductivity than yttria-doped zirconia, but it is very rarely used on account of its high price. 

The anodes consisting of a nickel catalyst and of cermet mixed with yttria-doped zirconia electrolyte that are used in conventional solid oxide fuel cells also lose their ability to work at lower temperatures because of a loss of conductivity by the ceramic. This suggests that, for the ceramic in the anode, a material having a higher conductivity at intermediate temperatures should be used. It was in fact shown that an anode made with a nickel/samaria-doped ceria cermet has a much lower polarization than the conventional variant. 

Nomura, K., Mizutani, Y., Kawai, M., Nakamura, Y., and Yamamoto, O. (2000). Aging and Raman scattering study of scandia and yttria doped zirconia. Solid State Ionics 132 ... 

Electrolytes require a high oxygen ionic conductivity and a dense microstructure to allow for gas separation of fuel and air compartment. Electronic conductivity is to be avoided since this would potentially short-circuit the SOFC. Chemical and thermomechanical stability of electrolytes with electrode materials is also an important requirement to assure long-term stability. Cubic 8 mol% yttria-doped zirconia is, due to its sufficiently and predominantly ionic conductivity, the state-of-the-art material used... 

Karthikeyan A, Chang CL, Ramanathan S (2006) High temperature conductivity studies on nanoscale yttria-doped zirconia thin films and size effects. Appl Phys Lett 89(18) 183116... 

Typical electrolyte materials for SOFCs are oxides with low valence element substitutions, sometimes named acceptor dopants [13, 95] which create oxygen vacancies through charge compensation. For SOFC applications, there are various materials that have been explored as electrolyte, yttria-doped zirconia (YSZ) and gadolinium-doped ceria (GDC) are the most common materials used for the oxideconducting electrolyte. Above 800 °C, YSZ becomes a conductor of oxygen ions (02-) zirconia-based SOFC operates between 800 and 1100 °C. The ionic conductivity of YSZ is 0.02 S m at 800 °C and 0.1 S cm at 1000 °C. A thin electrolyte (25-50 (im) ensures that the contribution of electrolyte to the ohmic loss in the SOFC is kept to a minimum. 

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