Temperature dependence of anisotropy of conductivity in oriented reticulate-doped systems
| Autor: | G Debrue, E El Shafee, J Ulanski, A Tracz, Robert Deltour |
|---|---|
| Rok vydání: | 1990 |
| Předmět: |
chemistry.chemical_classification
Materials science Condensed matter physics Mechanical Engineering Doping Isotropy Metals and Alloys Polymer Activation energy Conductivity Condensed Matter Physics Electronic Optical and Magnetic Materials Nuclear magnetic resonance chemistry Deflection (physics) Mechanics of Materials Materials Chemistry Perpendicular Anisotropy |
| Zdroj: | Synthetic Metals. 35:221-228 |
| ISSN: | 0379-6779 |
| DOI: | 10.1016/0379-6779(90)90046-n |
| Popis: | All macromolecular conducting systems with an oriented structure reported so far exhibit relatively low anisotropy of conductivity; the conducting network is continuous and the anisotropy results from different densities of the conducting paths in different directions. This is also true for oriented reticulate-doped polymers obtained by a zone-casting technique, as long as their anisotropy is low. However, when the zone-casting parameters are optimized, the resulting anisotropy is very large, even more than 106. While the ‘parallel’ conductivity is similar to that of isotropic samples, the much lower ‘perpendicular’ conductivity has very high activation energy; i.e. the anisotropy increases very strongly with decreasing temperature. The transition from ‘conducting’ to ‘non-conducting’ direction is not smooth. With increasing deflection from the parallel direction, the conductivity decreases relatively slowly and the increase in activation energy is also weak up to ≈70°, then both values change dramatically, approaching the value characteristic of the perpendicular direction. We discuss geometrical aspects of the observed behaviour, concluding that the anisotropy has macroscopic character because it results from the morphology and not from the internal anisotropy of the columnar CT complex crystals. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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