Mixed ionic and electronic conducting

Double Substitution In such processes, two substitutions take place simultaneously. For example, in perovskite oxides, La may be replaced by Sr at the same time as Co is replaced by Fe to give solid solutions Lai Sr Coi yFey03 5. These materials exhibit mixed ionic and electronic conduction at high temperatures and have been used in a number of applications, including solid oxide fuel cells and oxygen separation. 

Another problem that is common for all membrane-based solid-state sensors is the ill-defined membrane-metal interface. A large exchange current density is required to produce a reversible interface for a stable potentiometric sensor response. One approach to improving this interface is to use conducting polymers. Conducting polymers are electroactive n-conjugated polymers with mixed ionic and electronic conductivity. They... 

In this chapter the technological development in cathode materials, particularly the advances being made in the material s composition, fabrication, microstructure optimization, electrocatalytic activity, and stability of perovskite-based cathodes will be reviewed. The emphasis will be on the defect structure, conductivity, thermal expansion coefficient, and electrocatalytic activity of the extensively studied man-ganite-, cobaltite-, and ferrite-based perovskites. Alterative mixed ionic and electronic conducting perovskite-related oxides are discussed in relation to their potential application as cathodes for ITSOFCs. The interfacial reaction and compatibility of the perovskite-based cathode materials with electrolyte and metallic interconnect is also examined. Finally the degradation and performance stability of cathodes under SOFC operating conditions are described. 

This is not exactly the order as the electronic conductivity of the oxides, indicating that electrocatalytic activity of mixed ionic and electronic conducting (MIEC) oxides depends on other properties such as the oxygen exchange and ionic conductivities. 

The suitability of lanthanum nickelate as an SOFC cathode has been examined by Virkar s group [138], They showed that LN performed poorly as a single-phase cathode in an anode-supported YSZ cell. However, with an SDC/LN composite interlayer the performance of the LN cathode increased substantially and the maximum power density of the cell with a YSZ thin electrolyte (-8 pm) was -2.2 Wear2 at 800°C, considerably higher than 0.3 to 0.4 Wcm-2 of similar cells with only LN or SDC interlayer. The results are significant as it shows that the composite MIEC cathodes perform much better than single-phase MIEC in the case of LN despite its mixed ionic and electronic conductivity. 

In conclusion, mention should be made of glass electrodes exhibiting mixed, ionic and electronic conductances. A chalcogenide glass (28% Ge, 60% Se, 12%... 

In contrast, in most ion-selective membranes the charge conduction is done by ions. Thus, a mismatch between the charge-transfer carriers can exist at the noble metal/membrane interface. This is particularly true for polymer-based membranes, which are invariably ionic conductors. On the other hand, solid-state membranes that exhibit mixed ionic and electronic conductivity such as chalcogenide glasses, perovskites, and silver halides and conducting polymers (Lewenstam and Hulanicky, 1990) form good contact with noble metals. 

These examples and the general subjects mentioned above illustrate that ion conduction and the electrochemical properties of solids are particularly relevant in solid state ionics. Hence, the scope of this area considerably overlaps with the field of solid state electrochemistry, and the themes treated, for example, in textbooks on solid state electrochemistry [27-31] and books or journals on solid state ionics [1, 32] are very similar indeed. Regrettably, for many years solid state electrochemistry/solid state ionics on the one hand, and liquid electrochemistry on the other, developed separately. Although developments in the area of polymer electrolytes or the use of experimental techniques such as impedance spectroscopy have provided links between the two fields, researchers in both solid and liquid electrochemistry are frequently not acquainted with the research activities of the sister discipline. Similarities and differences between (inorganic) solid state electrochemistry and liquid electrochemistry are therefore emphasized in this review. In Sec. 2, for example, several aspects (non-stoichiometry, mixed ionic and electronic conduction, internal interfaces) are discussed that lead to an extraordinary complexity of electrolytes in solid state electrochemistry. 

Iwase, M., Ichise, E. and Jacob, K.T. (1984) Mixed ionic and electronic conduction in zirconia and its application in metallurgy. Adv. Ceram., 12 (Sci Technol Zirconia 2), 646-59. 

Sr-doped LaMnOj (LSM) cathode have been extensively investigated and developed as electrode materials. For oxygen reduction in SOFCs, mixed ionic and electronic conducting (MIEC) materials such as (La, Sr)(Co, FejOj (LSCF) show much higher electrochemical activity than that of LSM. However, MIEC materials based on cobaltites react readily with YSZ electrolytes to form resistive La2Zr207 and SrZrOj phases at the... 

Matsuzaki, K., Shikazono, N. Kasagi, N. Three-dimensional numerical analysis of mixed ionic and electronic conducting cathode reconstructed by focused ion beam scanning electron microscope. Journal of Power Sources 196, 3073-3082, doi 10.1016/j.jpowsour.2010.11.142 (2011). 

Solid solution electrode Solid compounds exhibiting mixed (ionic and electronic) conductivity, where it is possible to dissolve or remove additional ions. 

Jiang Q, Faraji S, Slade D A and Stagg-Williams S M (2010), A review of mixed ionic and electronic conducting ceramic membranes as oxygen sources for high-temperature reactors , Membr Sci Technol, 14,2iS-2Ti. 

The usual anode is a cermet (composite material made of a ceramic and a metal). Porous Ni-YSZ (yttria-stabilised zirconia) is the state-of-the-art electrode, presenting electronic and ionic conductivities in order to increase the number of reaction sites, called triple phase boundaries. It corresponds to the area where 0 , e and H2 are all present for the time required for the oxidation reaction to occur. No single phase has been found to completely fit all the requirements for an anode thermal and chemical compatibilities with the electrolyte, mixed ionic and electronic conductivity, high electro-catalytic activity and stability in reductive atmosphere. 

Oxygen separation by using a membrane is expected to be a real possibility, thanks to developments in mixed ionic and electronic conductors (MIECs). With mixed ionic and electronic conduction, oxide-ion conductors selectively permeate oxygen as a form of oxide ion. The mixed oxide-ion and electronic conductors used for this purpose are referred to as oxygen-permeable membranes. An oxygen-permeable membrane subjected to an oxygen potential gradient at elevated temperatures of around 700—1000 °C leads to the ambipolar conduction of oxide ions and electrons, as shown... 

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