Chemical Degradation in Thermally Treated Ferrite/Superconductor Multiphase Materials: Modeling Parameters
✍ Scribed by Agnes Kopia-Zastawa; I. Suliga; A. Siwek; J. Kusinski; S. Villain; M.A. Fremy; M.H. Pischedda; J.R. Gavarri
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- English
- Weight
- 633 KB
- Volume
- 160
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
Solid state chemical evolutions are studied in the case of superconductor/ferrite composites as a function of time and temperature. Pellets have been fabricated from ferrite NiFe 2 O 4 and superconducting cuprate Bi 1.6 Pb 0.4 Sr 2 Ca 2 Cu 3 O 10؉X (noted as Bi-2223). Two types of experimental approaches are presented: high-temperature electrical complex impedance spectroscopy, and EDAX analyses performed from scanning electron microscopy. From the in situ electrical analyses, two steps in the solid state chemical evolutions have been evidenced for the 5rst time. They can be associated with two types of solid state reactions: (i) direct reactions between the ferrite phase and the superconducting matrix and (ii) a self-degradation of the superconducting phase probably associated with a homogenization of elements. The electrical analyses are modeled using two types of kinetics parameters. From the EDAX analyses, the local distribution of each element is determined. The concentration pro5les found for the various elements (Ni, Fe, Bi, Sr, Ca, Cu) are interpreted in terms of a virtual di4usion law involving virtual D* coe7cients. These coe7cients are found to be of about 10 ؊11 (cm 2 /s) in the range 800+8303 3C.