This thesis describes the convenient routes and the preparation conditions (temperature, oxygen partial presssure) which lead to the formation of single phase materials within the quaternary system Cu-Ni-Fe-O. The investigated compositions are the solid solutions CuxNi1-xFe2O4, the ferrites occurring in the phase triangle Cu0.5Ni0.5Fe2O4 -Cu0.9Fe2.1O4 - Cu0.5Fe2.5O4 and some copper-nickel oxide solid solutions. Three synthesis routes have been used, namely (i) the preparation and the thermal decomposition of freeze-dried carboxylate precursors, (ii) the preparation and the oxidation of intermetallic phases and (iii) the preparation and the heat treatment in air of mixed oxide/metallic powders. The thermal decomposition of freeze-dried Cu-Ni-Fe formate has been found as a suitable method for preparing single spinel phases within the Cu-Ni-Fe-O system. In comparison with the conventional solid state reaction, the required temperature is much lower. Concerning the solid solution CuxNi1-xFe2O4 , a single phase spinel is formed at 1000¢XC for x < 0.7; for CuO is identified as second phase. In this latter range the formation of a pure phase required an increase of the iron content in the mixture. The other single spinel phases in the phase triangle Cu0.5Ni0.5Fe2O4 - Cu0.9Fe2.1O4 - Cu0.5Fe2.5O4 have been synthesized under special synthesis p(O2)/T-conditions. For copper ferrites Cu1-xFe2+xO4 with x ? 0.1, 0.2, 0.33, 0.4 and 0.5, the change in the conductivity with the temperature is irreversible. The deviation from the linearity of the conductivity ?ã as a function of the temperature occurs due to the thermal history of these samples. The saturation magnetic moment (nB) at 5K, of some synthesized CuxNi1-xFe2O4 compounds has been determined. It has been found that nB increases with the nickel content in the ferrite sample.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:24443 |
| Date | 15 December 2004 |
| Creators | Kenfack, Flaurance |
| Contributors | Langbein, Hubert, Ullmann, Helmut, Roewer, Gerhard |
| Publisher | Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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