Oxygen ion vacancies

Voltage Cell Type Oxygen Sensor The operation of the zirconia oxygen sensor utilizes the conduction of oxygen ions by virtue of anion or oxygen ion vacancies in the crystalline lattice. " The anion vacancies are created when the... 

At low oxygen partial pressures an equilibrium is established between lattice oxygen, gas phase oxygen, oxygen ion vacancies and free electrons and conduction is n-type. 

Oo denotes a lattice oxygen, Vo denotes an oxygen ion vacancy with an effective double positive charge and e denotes an electron. 

Over a large range partial pressures of oxygen ionic conductivity dominates and the material behaves as a solid electrolyte. Under these conditions there is an equilibrium established between oxygen ion vacancies, interstitial oxygen ions and lattice oxygen. 

SS3). On zinc oxide, on the other hand, the donor sites have been associated with Zn+ ions or oxygen ion vacancies with trapped electrons (334). 

As a result oxygen ion vacancies V and excess electrons e are formed [xxiv]. On the other hand, by incorporation of oxygen into the lattice, defect electrons (holes) are generated... 

The substitutional cation dopant (i.e., Y zr", Cazr) is compensated in the crystal lattice by an appropriate concentration of oxygen ion vacancies (i.e., Vij). Typical dopant concentrations for optimum conductivity are T3-15 mol % CaO and 8-10 mol%... 

These dopants also stabilize the crystal structure in the cubic fluorite phase at the sintering ( 1450°C) and in-service operating temperatures (600-1100°). The mechanism of ionic conduction involves migration of ions in the anion sublattice by exchange with oxygen ion vacancies. The 0 ion conductivity of yttria-stabilized ziroconia at 1100°C is comparable that of Na ion conductivity in jS"-alumina at 300° C. 

Yttria-doped( 20 mol% Y2O3) cerium oxide also has a higher 0 ion conductivity than yttria-stabilized zirconia ( factors of 11-18 at 600°C), which would make it an attractive choice for an electrolyte at lower temperatures (< 800 C) However, doped cerium oxides tend to undergo reduction, with formation of trivalent cerium ions and oxygen ion vacancies, V 6 leading to the onset of electronic conductivity according to ... 

The two defects with markers were identified rather simply. The slow-bleaching one had an ESR signal identical with that of the previously known F center (39) (an electron in an oxygen-ion vacancy) and was therefore that site. The other one had an ESR signal that differed in a way to suggest a site similar to an F center but on the surface. This, called an S center (for surface ), should show an asymmetric ESR absorption because of the surface location. The rapidity of the bleaching and adsorption was further evidence that it was a surface defect. 

The system Sr3Fe20g 7 is closely related to SrFeOs [181]. In this instance in a sample of Sr3Fe206 2 it is possible to detect an appreciable quadrupole splitting at the Fe + ion as a result of oxygen ion vacancies (Fig. 10.20). The fact that the iron(IV) spectrum is not quadrupole split implies that vacancies... 

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