| Autor: |
V. C. Mahajan, M. G. Patil, B. V. Bhise, S. D. Lotke, S. A. Patil |
| Rok vydání: |
1994 |
| Předmět: |
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| Zdroj: |
Solid State Communications. 91:667-670 |
| ISSN: |
0038-1098 |
| DOI: |
10.1016/0038-1098(94)90568-1 |
| Popis: |
The electrical resistivity (ϱ) and thermoelectric power (α) as a function of temperature for Cd0.5Ni0.5+xTixFe2−2xO4 system have been studied. It is observed that the resistivity (ϱ) increases slowly with increasing Ti content up to x = 0.2 and monotonously above x > 0.2. This is explained on the basis of localization phenomenon due to Ti which hinders the Verwey-de-Boer mechanism between Fe3+ → Fe2+ and Ni3+ → Ni2+ ions at B-site in the spinel up to x = 0.2. For x > 0.2 the inhomogeneous distribution of conduction between Ni3+ → Ni2+ ions in oxygen rich regions and between Fe2+ → Fe3+ ions in oxygen poor regions may take place by different mechanism. Ti4+ ions at B-site can also act as scattering center which hinders this mechanism. The variation of α with Ti and with temperature suggest that the oxygen poor and oxygen rich regions occur in these ferrites. Activation energies in the para (Ep) region are greater than the ferro-region (EF). This indicates the effect of magnetic ordering on conduction behaviour. The proportionality constant ΔE = AKTc(ΔE = Ep - EF) is 4 for x 0.2 Ti. This is related to oxygen content in the ferrites. The polaron hopping model is used to discuss the conduction phenomenon for these samples. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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