Conductivities in perovskites

S. Sekido, H. Tachibana, Y. Yamamura and T. Kambara, Electric-ionic conductivity in perovskite-type oxides, SrxLai-xCoi-yFey03-8- Solid State Ionics, 37 (1990) 253-259. 

In the case of perovskite structure, a part of Rare Earths or transition metal is substituted by alkali earth metal. The positive charge for fluorite and perovskite is deficient because of the substitution for the both of fluorite and perovskite. The charge in crystal is kept neutral by the formation of oxygen vacancy for fluorite. And the valence change of transition metal for perovskite keeps the neutral charge in crystal. As a result, the oxide ion conductivity in fluorite structure and the electrical conductivity in perovskite appear. 

In this chapter the focus is upon electronic conductivity in perovskites. The electrons in perovskites are believed to be strongly correlated that is, they do not behave as a classical electron gas, but are the subject to electron-electron interactions. This leads to considerable modification of the collective electron behaviour of the conduction electrons, resulting in metal-insulator transitions, high-temperature superconductivity, half-metals and colossal magnetoresistance (CMR). The effects of strong correlation are important for the 3d, 4d and4f elements. In many ways the topics described here are thus a continuation of the previous chapter on magnetic perovskites, and in truth the two subject areas cannot be separated in a hard and fast maimer. 

The current state of proton conductivity in perovskites has been discussed recently in detail by Wakamura [128]. 

Takahashi, T., and Iwahara, H. (1980). Solid-state ionics protonic conduction in perovskite type oxide solid solutions. Revue de Chimie minerale 17 243-233. 

Takahashi T, Iwahara H (1971) Ionic conduction in perovskite-type oxide solid solution and its application to the solid electrolyte fuel cell. Energy Convers 11 105-111... 

The conductivity in perovskites is a direct function of the concentration of ionic species, especially vacancies, Q, and the concentration of mobile electrons, n, and holes, p, available in the material. The concentration of vacancies is often related to the crystal structure of the material, whereas the electronic bandgap conditions to the concentration of mobile electrons and holes. Overall, the total conductivity of a perovskite, <7t> can be expressed as follows ... 

Ishihara, T. (2009). Oxide Ion Conductivity in Perovskite Oxide for SOFC Electrolyte in T. Ishihara (ed.) Perovskite Oxide for Solid Oxide Fuel Cells. Springer. London. 65-66. 

Table 3.1 Examples of ionic conduction in perovskite-type compounds...

Early Studies on Ionic Conduction in Perovskite-Type Oxides... 

Most of the possible combinations of large A cations and smaller B ions, which is needed to form perovskite-type oxides ABO3, had been tried by 1955, as described by F.S. Galasso in his famous book [2] entitled Structure, Properties and Preparation of Perovskite-Type Compounds, published in 1969. This book compiled almost all available data at that time concerning structure, properties, and preparation of perovskite-type compounds. In this book, although lattice defects in the perovskite-type crystal were described, the author did not touch on ionic conduction in the perovskite except for a very brief description of BaTiOs- However, in the 1960s, several pioneering studies on ionic conduction in perovskite-type oxides were performed. 

Ionic conduction in perovskite-type oxides was first a source of interest in ferroelectric materials. S. Swanson showed that DC conductivity of BaTiOs ceramics was significantly influenced by their fabrication history, which suggests that there would be an intimate relationship between the solid-state reactions of raw materials and ionic conduction [3]. In the 1960s, when research and development of perovskite-type oxides as a dielectric or ferroelectric material such as BaTiOs and PbTii xZrxOs had become active, some of the researchers paid attention to the conduction behavior of these perovskite-type oxides. They... 

Oxide Ion Conductivity in Perovskite Oxide for SOFC Electrolyte... 

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