Point Defects and Transport in Small Polaron Systems
A general defect equation has been developed which can describe defect phenomena in systems with variable valence cations (e.g. transition metals) which exhibit small polaron conduction. The types of defect phenomena considered include isolated point defects (vacancies), charged defect clusters (vacancy/interstitial), neutral clusters which link and produce percolation networks, and oxygenation (intercalation) where oxygen insertion does not result in the formation of cation vacancies but is still charge compensated by the variable valence cations. The bulk cation valence ratio (isolated defects, charged clusters, oxygen intercalated structures) and the local cation valence ratio (neutral cluster networks) can be studied via the electrical properties (conductivity, thermopower.) Examples are taken from the systems: Co1−δO, La2−xBaxCuo4 and YBa2Cu3O6+Y.
KeywordsTransition Metal Oxide Small Polaron Neutral Cluster Mixed Valence Compound Small Polaron Conduction
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