Improvement of the magnetic and electric properties of Cu-Zn ferrites
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IMPROVEMENT OF THE MAGNETIC AND ELECTRIC PROPERTIES OF Cu – Zn FERRITES A. M. Samy We study Cu – Zn polycrystalline ferrites substituted with rare-earth ions. For substituted samples ( R = Nd, Sm, and Gd ), the initial magnetic permeability and homogeneity increase as compared with nonsubstituted samples. At the same time, the magnetization and energy losses decrease for all substituted samples. The specific resistance increases only for samples with R = La and Nd. The grain sizes increase for all substituted samples (as compared with nonsubstituted) except the samples with R = La and Nd. It is shown that the Curie temperature is almost constant and does not depend on the type of substituted rare-earth ions.
Ferrites are very important materials in technology. They are used in radio, TV, microwave, and satellite communications, digital recording, and as permanent magnets. As advantages of ferrites, one can mention their higher efficiency, lower costs, and easier manufacturing as compared with metals. Sattar et al. studied the electric and magnetic properties of a single phase Cu0.5 Zn0.5 Fe2 – x R x O4 , where x = 0.0 and 0.1 and R = La, Nd, Sm, Gd, and Dy [1, 2]. It was discovered that a Sm-substituted sample showed the highest initial permeability. Later, Sattar and the author studied the magnetic and electric resistivity properties of Cu0.5 Zn0.5 Fe2 – x Smx O4 , where x varies from 0.0 to 0.1 but for a different presintering time. It was reported that the sample with x = 0.02 had the highest initial permeability and Curie temperature [3]. Furthermore, the electric resistivity increased with the Sm content of the material. These results are very important from the technological point of view. Therefore an attempt to improve the magnetic and electric properties of Cu – Zn ferrites substituted with different rare-earth ions with the same percentage x = 0.02 and the same preparation conditions as those described in [2] was undertaken. Experimental Techniques Compositions with the following chemical formula: Cu0.5 Zn0.5 Fe2 – x R x O4 , where x = 0.0 and 0.02 and R = La, Nd, Sm, and Dy, were prepared by using the ceramic technique. High-purity oxides with 99.9% of Cu O, Zn O, Fe2 O3 , and R2 O3 were mixed together according to their molecular weights. The mixture of each sample was ground to a very fine powder and then presintered at 900°C for 30 h. The presintered powders were ground again and pressed under a pressure of 400 kPa into toroids and discs. Then they were finally sintered at 1000°C for 6 h in two cycles and slowly cooled down to room temperature. The X-ray diffraction patterns were prepared by using a PW-3710 diffractometer with CuKα radiation. The porosity percentage P (m %) was calculated according to the relation d P = 100 1 − , dx Physics Department, Faculty of Science, Ain Shams University, Abbassia, Cairo, Egypt. Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 4, pp. 84–88, July–August, 2004. Original article submitted March 3, 2003. 1068–820X/04/4004–0529
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