Other Ferrites

A W/O microemulsion synthesis of Fe203, Ni, sZn5Fe204 and Mn, 5ZngFe204 particles was recently reported by Yener and Giesche [314]. The synthesis was carried out by the two-microemulsion technique using AOT/isooctane/aqueous phase, where the aqueous phase was either 

Note that the value of 5 was taken as 0.5. The synthesis was performed at 5°-25°C in all cases (15 C was found to be optimal) and the equilibration time was at least 48h. The products were washed with methanol and centrifuged, followed by drying at 85°C and calcination up to 1200°C. 

When the pure iron oxide particles were calcined, indications of hematite formation were already present at 450°C/6h, but well-crystallized a-Fe203 was obtained at 600°C/6h. In case of the two doped oxides, no control of atmosphere was required for calcination up to 600°C/25 min, and the products were of the spinel structure. Above 600°C (800°C and above for 3-5 h), hematite appeared as an additional phase. The particles obtained after calcination were rather large (overall span for the three species 2Q-150 nm), showing significant growth from the as-prepared stage. As an example, the Fe203 particles increased in size from 10-30 nm before calcination to 40-85 nm at 600°C/6 h. 

Doping BiFeOs rnay improve its photocatalytic performances. The lattice insertion of Sr led to a decrease of the bandgap from 2.26 to 2.15 eV with the 

Perovskite semiconductors and related materials, among a large number of other applications, are widely used in photocatalysis, especially in the photogeneration of hydrogen. Their adaptation includes new preparation strategies, supporting the active phase, development of composite materials, doping with anions and cations to induce lattice defects, and the exploitation of the surface plasmon resonance of the noble metals. 

As for other materials, the research on perovskite photocatalysts is in a continuous effort to improve their properties and their applications to the sunlight irradiation, a virtually inexhaustible green energy source. 

1 Fujishima, A. and Honda, K. (1972) Electrochemical photolysis of water at a semiconductor electrode. Nature, 

3 Herrmann, J.-M. (1999) Heterogeneous photocatalysis fundamentals and applications to the removal of various types of aqueous pollutants. Catal. 

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These results can be contrasted with results obtained using a less stringent equilibrium criterion of = 0.0005 S cm-1 min-1 as shown in the open circle data in Fig. 6. A large discrepancy is observed in the middle- o2 region. A difference between the measured values of Po2 by the sensors at the top and bottom of the cell of more than one order of magnitude in p0 was found under these conditions. In general, the p0 difference between the two sensors is slow to converge due to the slow equilibrium kinetics and consequently, both conductivity and log p0 difference criteria are needed to ensure that equilibrium is reached. The open circle data in Fig. 6 are similar to results in other ferrite perovskite oxides and reflect nonequilibrium behavior.14 17... 

The Raman spectrum of cobalt ferrite single crystals excited by 532 nm laser line, attained at room temperature, is reproduced in Fig. 14.5. By performing the fitting of the Raman spectra displayed in Fig. 14.5, it would be possible to observe Raman bands at 183, 304, 469, 573, 627, and 696, listed in Table 14.2. Apart from Fc304, y-Fe203, and CoFc204, others ferrites such as NiFc204 and Fc3 . Zn - O4 which... 

Chemical-transport reactions have been used to prepare single crystals of triiron tetraoxide (magnetite) and other ferrites, which comprise the majority of all known ferrimagnetic mate-... 

The same transport procedure has been used to prepare crystals of other ferrites, such as NiFc204. 

Iron oxide nanoparticles are undoubtedly one of the most investigated nanoparticles owing to their importance in industrial and medical appUcations. Hematite nanoparticles are comparatively more stable and therefore have wider applications as well. While several methods are available for the synthesis of nanoparticles, the green synthesis routes are preferred, more so iu biological apphcations. It has beeu demoustrated that natural products such as polysaccharides can be employed as effective templates, both through sacrillcial and otherwise routes to generate mono-dispersed nanoparticles of below 20 run. Such methods are easy to adopt for other ferrite nauoparticles as well. Incidentally, some of the polysaccharide methods are facile and possibly simple for rephcation at industrial scales. 

Note We have done exactly these experiments on others ferrites i.e. zinc ferrite and manganese ferrite and have obtained for each of them optimum parameters. But to prevent long or repeated exposures and similar experiments, we reported only the experiments of nickel ferrite nanoparticles and for others ferrites we sufficed only to report of values (Table3). 

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