Solid ionic conductors

M. Armand, M. Gauthier in High Conductivity Solid Ionic Conductors (Ed. T. Takahashi), World Scientific, Singapore, 1989, p. 114. 

Figure 9. Compilation of the solid ionic conductors known at present. For references see Table 1.

H. Rickert, Solid Ionic Conductors Principles and Applications, Angew. Chem. Int. Ed. Engl. 17,37-46(1978). 

S. Bebelis, M. Makri, A. Buekenhoudt, J. Luyten, S. Brosda, P. Petrolekas, C. Pliangos, and C.G. Vayenas, Electrochemical activation of catalytic reactions using anionic, cationic and mixed conductors, Solid State Ionics 129, 33-46 (2000). 

Because of the high values of conductivity which in individual cases are found at room temperature, such compounds are often called superionic conductors or ionic superconductors but these designations are unfounded, and a more correct designation is solid ionic conductors. Strictly unipolar conduction is typical for all solid ionic conductors in the silver double salts, conduction is due to silver ion migration, whereas in the sodium polyaluminates, conduction is due to sodium ion migration. 

Conductivity Metals are good conductors of electricity and heat because electrons can move freely throughout the metallic structure. This freedom of movement is not possible in solid ionic compounds, because the valence electrons are held within the individual ionic bonds in the lattice. 

A method of characterising transport mechanisms in solid ionic conductors has been proposed which involves a comparison of a structural relaxation time, t, and a conductivity relaxation time, t . This differentiates between the amorphous glass electrolyte and the amorphous polymer electrolyte, the latter being a very poor conductor below the 7. A decoupling index has been defined where... 

Red hexagonal crystals or free-flowing fine red powder density 1.27 g/cm melts at 813°C an excellent solid ionic conductor conductivity dxlCL mho/cm at 227°C decomposes in water. 

Electrical conductivity can also be an important consideration in p3rrotechruc theory [7]. This phenomenon results from the presence of mobile electrons in the solid that migrate when an electrical potential is applied across the material. Metals are the best electrical conductors, while ionic and molecular solids are generally much poorer, serving well as insulators. 

Solid ionic conductors can also be used in the fabrication of solid state double-layer supercapacitors. An example is the device developed in the late 1960s by Gould Ionics which adopted a cell system using a silver-carbon electrode couple separated by the highly ionically conducting solid electrolyte RbAg4I5 (see Section 9.1) ... 

A large body of literature has been accumulated over the last three decades concerning so-called fast ionic conductors. Fast ionic conductors have an ionic conductivity (Fig. 15-8) comparable to that of moderately concentrated aqueous ionic solutions (ca. 0.1-1 moll1). Fast ionic conduction is found in solid electrolytes and semiconducting crystals. Although known for quite some time, these materials became really interesting when solids were discovered which showed the unexpected high... 

We summarize what is special with these prototype fast ion conductors with respect to transport and application. With their quasi-molten, partially filled cation sublattice, they can function similar to ion membranes in that they filter the mobile component ions in an applied electric field. In combination with an electron source (electrode), they can serve as component reservoirs. Considering the accuracy with which one can determine the electrical charge (10 s-10 6 A = 10 7 C 10-12mol (Zj = 1)), fast ionic conductors (solid electrolytes) can serve as very precise analytical tools. Solid state electrochemistry can be performed near room temperature, which is a great experimental advantage (e.g., for the study of the Hall-effect [J. Sohege, K. Funke (1984)] or the electrochemical Knudsen cell [N. Birks, H. Rickert (1963)]). The early volumes of the journal Solid State Ionics offer many pertinent applications. 

A second type of solid ionic conductors based around polyether compounds such as polyethylene oxide) (PEO) has been discovered and characterized. The polyethers can complex and stabilize lithium ions in organic media. They also dissolve salts such as L1CIO4 to produce conducting solid solutions. The use of these materials in rechargeable lithium-batteries has been proposed. 

Membranes from Polymeric Solid Ionic Conductors... 

Two types of solid ionic conductors are of special interest—those in which metallic cations such as lithium ions can be transported across the polymer membrane, and others in which protons can move from one side of the membrane to the other. The first... 

After 14 years on the faculty of Imperial College, Jacobs moved from London, England, to London, Ontario, where his research program focused on the optical and electrical properties of ionic crystals, as well as on the experimental and theoretical determination of thermodynamic and kinetic properties of crystal defects.213 Over the years his research interests have expanded to include several aspects of computer simulations of condensed matter.214 He has developed algorithms215 for molecular dynamics studies of non-ionic and ionic systems, and he has carried out simulations on systems as diverse as metals, solid ionic conductors, and ceramics. The simulation of the effects of radiation damage is a special interest. His recent interests include the study of perfect and imperfect crystals by means of quantum chemical methods. The corrosion of metals is being studied by both quantum chemical and molecular dynamics techniques. 

One of the exceptions was the discovery of high ionic conductivity in appropriately doped FaGa03.128 129 As in the other oxide ion conductors, its ionic conductivity depends on both the dopant level as well as on the nature of the dopant. A major difference to ceria and zirconia is the presence of two cations that can be substituted the detailed defect chemistry of such solid solutions is far from being fully understood. Co-doping of Sr on A sites and Mg on B-sites leads to an ionic conductivity of ca. 0.12—0.17 S cm 1 at 800°C,130-133 which is similar to doped ceria but considerably exceeds the value of YSZ (ca. 0.03 S cm 1 at 800°C80 81). The activation energy also varies with composition and can be as low as ca. 0.6 eV.130 131 At about 600-700°C, the... 

Salter, D.C. Monitoring human skin hydration in vivo using electrical impedance — a model of skin as a solid ionic conductor. Proceedings IX International Conference on Electrical Bio-Impedance and European Community Concerted Action on Impedance Tomography, Heidelberg, September 26-30, 1995, pp. 17-20. 

In the technology of ceramics, electronic conductors (semiconductors), ionic conductors (solid electrolytes) and mixed electronic-ionic conductors are encountered. In all cases the conductivity is likely to vary with temperature according to... 

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