Oxide ion mobility

When the binary rare-earth oxide fluorides are utilized in a solid-state fuel battery, they must often withstand at a high temperature of around 1000°C to exhibit sufficient oxide ion mobility, i.e. to supply appropriate electrical current. These... 

Diffusion coefficient and surface exchange coefficient measurements have been reported for the K2MF4 type oxide materials by a number of authors [4-8, 13-19] and have been complemented by electrochemical permeation measurements [20-27] all of which demonstrate the fast oxide ion conduction of hyperstoichiometric K2NiF4 type oxides. Early reports also demonstrate the relatively poor oxide ion mobility in those materials found to be hypostoichiometric [28,29]. Initial reports of the fast oxide ion conduction in La2Ni04+s [4, 6-8] have generated a number of further studies [13-19] regarding the optimization of composition and determination of the effects of anisotropy on the conduction properties of these materials. Each of these features will be discussed in more detail below. 

The kinetics of this Uansport, virtually of oxygen atoms tlrrough the solid, is determined by the diffusion coefficient of the less mobile oxide ions, and local... 

For iron in most oxidising environments, the PBR is approximately 2.2 and the scale formed is protective. The oxidation reaction forms a compact, adherent scale, the inner and outer surfaces of which are in thermodynamic equilibrium with the metal substrate and the environment respectively, and ion mobility through the scale is diffusion controlled. 

It is convenient for the purposes of this chapter initially to make a number of simplifying assumptions about the nature of the electrolytes under discussion. For example, Ag4RbIs will be assumed to be an ionic conductor with negligible electronic conductivity and with only the silver ion mobile. Likewise Na-jS-Al203 will be assumed to be a substance in which the only mobile charge is Na". Another simplifying assumption of a different sort which we will make is that the interfaces when formed do not, in general, have a third phase, e.g. an oxide film between the... 

Figure 25. Proton conductivity of various oxides, as calculated from data on proton concentrations and mobilities, according to Norby and Larring (the type of dopant is not indicated see ref 187 for source data). The conductivity of oxides with a perovskite-type structure are shown by bold lines, and the conductivity of the oxide ion conductor YSZ (yttria-stabilized zirconia) is shown for comparison, (reproduced with the kind permission of Annual Reviews, http //www.AnnualReviews.org).

MOS metal oxide sensor, MOSFET metal oxide semiconductor field-effect transistor, IR infrared, CP conducting polymer, QMS quartz crystal microbalance, IMS ion mobility spectrometry, BAW bulk acoustic wave, MS mass spectrometry, SAW siuface acoustic wave, REMPI-TOFMS resonance-enhanced multiphoton ionisation time-of-flight mass spectrometry... 

The mobility of lattice oxide ion under the working conditions was examined in the oxidation of propylene with 1802 for a series of... 

---