Zirconia, oxide-doped

The addition of cerium oxide, for example, to zirconia produces a material with exceptional toughness and good strength [29], Cerium oxide-doped zirconia is used also in thermal barrier spray coatings on metal surfaces(30]. 

Oxides exhibiting only high ion conductivity are mainly fluorite-related structures based on zirconia or ceria. Zirconia-based electrolytes are currently used in solid oxide fuel cells (SOFCs). The MIEC oxides are more attractive for separative membrane applications, and these oxides mainly belong to the following types fluorite-related oxides doped to improve their electron conduction, - ... 

It is considered that the bulk area specific resistance i o must be lower than l o = k/<7 = 0.15 Qcm, where L is the electrolyte thickness and a is its total conductivity, predominantly ionic [39]. At present, fabrication technology allows the preparation of reliable supported structures with film thicknesses in the range 10-15 pm consequently, the electrolyte ionic conductivity must be higher than 10 Scm. As shown in Figure 12.9, a few electrolytes (ceria-based oxides, stabihzed zirconias, and doped gallates) exceed this minimum ionic conductivity above 500 °C. 

In the present work the behaviour of zirconia samples doped with oxides of alkali metals and alkaline-earth metals was investigated, in order to better understand the role of both the nature and the amount of the doping cation. Li-, K-, Ca-, and Ba-doped zirconia samples were prepared. Their surface acid-base properties were assessed by means of adsorption microcalorimetry, using ammonia and carbon dioxide as probe molecules. Their catalytic activity for the 4-methylpentan-2-ol dehydration was tested in a flow microreactor. 

The ceramic electrolyte is based on zirconia (Zr02) or ceria (Ce02), each of which is an electronic insulator but is conductive towards oxide ions (0 ) at high temperatures. This conductivity is achieved by doping the chosen oxide with ions of lower valency. For instance, when zirconia is doped with yttrium ions (Y ), oxide ion vacancies are formed in the parent lattice to compensate for the charge difference, i.e.,... 

A solid oxide fuel cell consists of a cathode (at which O2 from the air is reduced to and an anode (at which H2 is oxidized), and an electrolyte. The cell operates at 1300K. Explain why stabilized zirconia Zr02 doped with CaO or Y2O3 is a suitable material for the electrolyte. What is the product at the anode ... 

The calcination temperature plays an important role in the stabilization of a particular chromium oxidation state. This state seems to be responsible of the improvement of the catalytic performances of sulfated zirconia aerogels doped with chromium (Figure 6.5) [45]. 

Figure 6.5. influence of chromium oxidation state on the catalytic activity of sulfated zirconia aerogels doped with chromium A. AZ873/Cr(III)-Al B. AZ873/Cr(V)-Al [45],... 

Indium tin oxide, titania, zirconia, tungsten oxide, doped oxides Ceramic coatings, transparent conductive films... 

Aluminum silicate, alumina, mixed metal oxides, zirconia, metal doped oxides, zeolites Catalysts... 

Liu, Q.L., Khor, KA., Chan, SXI., and Chen, X.J. (2006) Anode-supported solid oxide fuel cell with yttria-stabilized zirconia/gadolinia-doped ceria bilayer electrolyte prepared by wet ceramic cosintering process. J. Power Sources,... 

Titania-zirconia mixed oxides doped with vanadium and cerium oxides were also explored. The Ti02-Zr02 mixed oxide support, synthesized by a co-precipitation... 

The development of the ideas mentioned above has taken place over more than a century, in 1890, it was not yet clear what electrical conduction was. The electron had not quite been defined. Metals were known to conduct electricity in accord with Ohm s law, and aqueous ionic solutions were known to conduct larger entities called ions. Nernst then made the breakthrough of observing various types of conduction in stabilised zirconia, that is zirconium oxide doped with several mole per cent of calcla, magnesia, yttria, etc. Nernst found that stabilised zirconia was an insulator at room temperature, conducted ions in red hot conditions, from 600 to 1000°C and then became an electronic and ionic conductor at white heat, around 1500°C, He patented an incandescent electric light made from a zirconia filament and sold this invention which he had been using to illuminate his home [1-3], He praised the simultaneous invention of the telephone because it enabled him to call his wife to switch on the light device while he travelled back from the university. The heat-up time was a problem even then [4],... 

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