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Ceramic Method (ceramic + method)
Selected AbstractsInfluence of the starting powders on the synthesis of nickel ferriteCRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2006F. Kenfack Abstract The thermal decomposition of freeze-dried nickel(II)-iron(III) formate was investigated by means of DTA, TG, mass spectrometry and X-ray powder diffractometry. For the preparation of homogeneous freeze-dried nickel(II)-iron(III) formate precursors, a rigorous control of nickel ion concentration in the precursor solution was required. The decomposition of the reactive nickel(II)-iron(III) formate does not only reflect aspects of single formates, but also an interaction between components which lowers the decomposition temperature. Crystalline nickel ferrite powders were obtained at 600-800°C. This temperature is quite lower than 1100°C employed for the ceramic method. In the presence of air, the regeneration of nickel ferrite from the taenite phase (,Ni,Fe) is accomplished at 800°C. This temperature is also 300°C below the temperature employed when the mixtures NiO:,-Fe2O3 or Ni:2Fe are the starting powders. The main reason for the high reactivity of the freeze-dried formates and the taenite alloy is the large homogeneity of these precursors. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Enhanced Permeability and Dielectric Constant of NiZn Ferrite Synthesized in Nanocrystalline Form by a Combustion MethodJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2007Sasanka Deka The performance parameters of Ni0.5Zn0.5Fe2O4, synthesized in the nanocrystalline form by an autocombustion method, have been investigated. The sample sintered at 1200°C, with Bi2O3 as additive shows a very high value of initial permeability ,,i of >400 at 1 MHz, with low loss. Similarly, a very high dielectric constant is obtained at lower frequencies. The results show that optimum magnetic and electrical properties can be achieved for the NiZn ferrite nanocrystalline powders synthesized by the present autocombustion method and sintered at a relatively lower temperature of 1200°C when compared with a temperature of 1400°C required for the materials synthesized by the conventional ceramic method. [source] Solid-Solution Formation in the Synthesis of Fe-ZirconJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2004Enrique Carreto Cortés To investigate solid-solution formation in the iron-doped silicate (zircon) system, different samples were prepared by the ceramic method with addition of LiF as a mineralizer. The results of X-ray powder diffraction (XRD), 57Fe Mössbauer, and UV,visible spectroscopy showed that in the as-prepared samples, only a small fraction of iron, i.e., about 2.5 mol%, is hosted in the zircon structure as paramagnetic Fe3+ species, while the remaining Fe3+ cations form magnetic ,-Fe2O3 particles that are trapped in the zircon matrix. [source] Dielectric and magnetic properties of citrate-route-processed Li,Co spinel ferritesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2007Nutan Gupta Abstract Cobalt-substituted lithium ferrites (with general composition Li0.5,x /2CoxFe2.5,x /2O4, where x = 0.0, 0.2, 0.4, 0.5 and 0.6) were prepared at lower processing temperatures (,600 °C) by the citrate route. The single-phase spinel structure was confirmed by X-ray diffraction. The average particle size of calcined powders calculated by the Scherrer formula is estimated to be 8,90 nm, whereas an average particle size of ,20 nm is observed from TEM for Co concentration x = 0.5. Average grain sizes from SEM micrographs of pellets sintered at 1000 °C (1 h) are observed to be 0.5,1 ,m, much smaller than the size reported for the standard ceramic method (2.1,6.8 ,m). The experimental density is observed to be 3.59,4.47 gm/cm3, which is greater than 85% of the densities evaluated from XRD. Compared with the standard ceramic method, lower dielectric constant (10,103) and higher dc resistivity (105,1010 , cm) is observed for Li,Co ferrites prepared by the citrate route. Improved magnetic properties, such as higher saturation magnetization (38,79 emu g,1) and Curie temperature (535 to 620 °C) are also investigated for the citrate-route-processed samples. These results demonstrate promising features of Li,Co ferrites in microwave applications. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||