Yttrium-stabilized zirconia

Anion Vacancies If the cation of the host structure has a higher charge than the replacing cation, electroneutrality may be maintained by introducing vacancies into the anion sublattice. The best-known examples of anion vacancies occur in the stabilized zirconia, such as calcium- or yttrium-stabilized zirconia. The high-temperature... 

Liu J and Barnett SA. Thin yttrium-stabilized zirconia electrolyte solid oxide fuel cells by centrifugal casting. J Am Ceram Soc 2002 85 3096-3098. 

Fig. 6.40 Potentiometric gas sensor based on yttrium-stabilized zirconia (YSZ)...

Yttrium stabilized zirconia (Zr02-Y203) as an electrolyte for reduction of molecular oxygen at elevated temperatures (400-800°C) has been already discussed in Section 6.23.4. In fact, both the reduction of oxygen and the oxidation of the oxide ion at the Pt/zirconia interface is reversible and the transport of both species in zirconia is so rapid it is possible to construct an electrochemical oxygen pump, which is the heart of the limiting current oxygen sensor described in this chapter (Saji, 1987). The overall electrochemical reaction that takes place at the porous Pt electrode is... 

A controlled modification of the rate and selectivity of surface reactions on heterogeneous metal or metal oxide catalysts is a well-studied topic. Dopants and metal-support interactions have frequently been applied to improve catalytic performance. Studies on the electric control of catalytic activity, in which reactants were fed over a catalyst interfaced with O2--, Na+-, or H+-conducting solid electrolytes like yttrium-stabilized zirconia (or electronic-ionic conducting supports like Ti02 and Ce02), have led to the discovery of non-Faradaic electrochemical modification of catalytic activity (NEMCA, Stoukides and Vayenas, 1981), in which catalytic activity and selectivity were both found to depend strongly on the electric potential of the catalyst potential, with an increase in catalytic rate exceeding the rate expected on the basis of Faradaic ion flux by up to five orders of... 

The Lambda probe consists of a solid-state electrolyte (yttrium-stabilized zirconia) that is covered with porous platinum - electrodes on the inside (1) and outside (2) (see Fig.). 

Sensor. The control of the exhaust composition was essential to maintain the air-to-fuel ratio close to stoichiometric for simultaneous conversion of all three pollutants. This control came about with the invention of the 02 sensor.21,22 The sensor head of this device was installed in the exhaust immediately at the inlet to the catalyst and was able to measure the 02 content instantly and precisely. It generates a voltage consistent with the Nemst equation in which the partial pressure of 02 (P02)exhaust in the exhaust develops a voltage (E) relative to a reference. The exhaust electrode was Pt deposited on a solid oxygen ion conductor of yttrium-stabilized zirconia (Zr02). The reference electrode, also Pt, was deposited on the opposite side of the electrolyte but was physically mounted outside the exhaust and sensed the partial pressure (P02)ref in the atmosphere. E0 is the standard state or thermodynamic voltage. R is the universal gas constant, T the absolute temperature, n the number of electrons transferred in the process, and F the Faraday constant. 

Among the various electrolytes, yttrium stabilized zirconia (YSZ) has been developed, for use in high-temperature fuel cells and oxygen sensors similarly, various S( S")-alumina materials are in development for sodium sulfur batteries. 

Figure 2.57. Comparison of unit cells of cubic zirconia and yttrium stabilized zirconia (YSZ), showing transport of oxide ions through a lattice via vacant sites in neighboring YSZ unit cells.

Growth by vapor deposition and oxidation (VDO) of Ce onto a substrate has been used successfully. The simplicity of this approach and its ability to be integrated into UHV systems designed for multiple surface diagnostic methods makes this a common technique for surface studies of chemisorption and surface reaction studies on model catalytic surfaces. Many of the ceria films used in work described below were produced in this way. Ce deposition and oxygen exposure (oxidation) may be performed simultaneously or sequentially. - Single crystal metals (Pt, Cu, Pd, Ni, and Ru ) and oxides, including yttrium-stabilized zirconia (YSZ), and sapphire, have been used as substrates for this approach. Such films have been... 

In spite of the extensive applications of yttrium-stabilized zirconia (YSZ)-based solid electrolytes, many details of their conductivity mechanism and its... 

HC, hydrocarbons YSZ, yttrium stabilized zirconia S/C, steam-to-carbon ratio. 

Graf, P.O., Mojet, B.L., van Ommen, J.G., and Lefferts, L. Comparative study of steam reforming of methane, ethane and ethylene on Pt, Rh and Pd supported on yttrium-stabilized zirconia. Applied Catalysis. A, General, 2007, 332 (2), 310. 

In this chapter, attention will be focused on hybrid materials involving polymeric species. However, it should be noted that a wide variety of composites are currently under research—for instance, NiO plus yttrium-stabilized zirconia (Lee et al., 2001)... 

Complex FCC oxides of the fluorite type represent oxygen-conduction solid electrolytes (SOE s). They comprise a typical class of materials for the manufacture of sensors of oxygen activity in complex gas mixtures, oxygen pumps, electrolyzers and high-temperature fuel elements. These materials are based on doped oxides of cerium and thorium, zirconium and hafnium, and bismuth oxide. Materials based on zirconium oxide, for example, yttrium stabilized zirconia (YSZ) are the most known and studied among them. This fact is explained both by their processibility and a wide spectrum of practical applications and by the possibility to conduct studies on single crystals, which have the commercial name "fianites" and are used in jewelry. 

Refining of the particle size can be achieved by etching of bulk sample. For example, the nanosize zirconia powder doped with yttrium has been prepared by etching of yttrium containing polycrystalline BaZrOs or NaaZrOs [15]. Preliminary sintered ceramics of BaZrOs or Na2Zr03 doped with yttrium was subjected to hydrothermal treatment to eliminate the undesirable ions of Ba + or Na+ in nitric acid solution or supercritical water. The etching precipitate represents yttrium-stabilized zirconia nanopowder with particle size of 3-15 nm. 

Typical ferroelastic is zirconia, which can be obtained from the unstable compounds in the form of powders. As a result of calcination of zirconium oxalate or hydroxide under non-isothermal conditions, the extreme dependence of the specific surface area of zirconia nanoparticles on heating rate has been revealed. This dependence has been confirmed for both pure Zr02 and stabilized with different dopants (Fig. 5.21). In accordance with [301], the maximum surface area for the amorphous powders of yttrium stabilized zirconia with particle size less than 5 nm, growing during crystallization and coarsening to 8-10 nm, depends on the heating mode. 

J. Zhu, J. G. Ommen, and L. Lefferts. Reaction scheme of partial oxidation of methane to synthesis gas over yttrium-stabilized zirconia. J. Catalysis 225, 388-397. 

Andersen A G, Hayakawa T, Snzuki K, Shimizu M and Takehira K (1994), Electrochemical methane conversion over SrFe03 perovskite on an yttrium stabilized zirconia membrane , Catal Lett, 27,221-233. 

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