| Manganese-Zinc ferrite, due to the great application value and the long-term basic research, has been widely used in the fields of computer, network communication, space transportation and so on, meanwhile, has interested scientists in the fields of condensed matter physics and solid-state chemistry.In this paper, MnxZn1-xFe2O4 and a-Fe2O3 nanometer powders were prepared by chemical coprecipitation method; the magnetic properties of MnxZn1-xFe2O4 nanometer powders and pellets, especially, the magnetic properties and the temperature dependence of resistivity of (MnxZn1-xFe2O4)1-y/(a-Fe2O3)y composites were systematically studied. Compared the (MnxZn1-xFe2O4)1-y(a-Fe2O3)y composites with the MnxZn1-xFe2O4 pellets, the result show that, not only the high frequency soft magnetic properties, but also the thermo-sensitivity of resistivity were enhanced. Hence, it offers a new clue to improve the properties of Manganese-Zinc ferrite. The main work was as follows:1. The crystal structure, the magnetic and the electrical properties of powder and pellet ferrite samples(1). MnxZn1-xFe2O4, NiFe2O4 and CoFe2O4 nanometer powders were prepared by chemical coprecipitation method. The results measuring morphology and phase structure confirm that the crystal structure of powder samples is same as that of the bulk polycrystalline materials. With the increase of reaction temperature and heat treatment temperature, the particle diameter increases from 30 run to 150 nm, meanwhile, the crystallized degree of the particles is improved markedly.(2). The results of the powders measured by vibrating sample magnetometer (VSM) show that the higher reaction temperature and heat treatment temperature are, the better the magnetic properties are. Moreover, if the preparing condition is same, the saturation magnetization intensity of MnxZni.^Fe2O4 increases gradually with adding Mn contents (x=0.00,0.15,0.35, 0.60,1.00).(3). After pressing the above-mentioned powders into pellets under the pressure of 672 Mpa, sintering the pellets at the 1673 K using ceramic technology, we prepared the nanometerpellet samples and measured the temperature dependence of resistivity. We found that with the increase of measurement temperature, the resistivity of the pellet samples decreases; additionally, the resistivity of the pellet samples decreases with lessening Mn contents; among the pellet samples of MnxZn1-xFe2O4, NiFe2O4 and CoFe2O4, the resistivity of ZnFe2O4 sample is the most sensitive to temperature, the resistivity of MnFe2O4 sample is the most stable to temperature.2. Magnetic and electrical properties of (MnxZn1-xFe2O4)1-y/(a-Fe2O3)y nanometer composite samples(1). a-Fe2O3 nanometer powders were prepared by chemical coprecipitation method, the crystal size can be controlled about 30 nm. After doping a-Fe2O3 powders into MnxZn1-xO4 powders, pressing the mixed powders into pellets under the pressure of 672 Mpa, lastly the nanometer composite samples were gained after sintering the pellets at the 1673 K using ceramic technology.(2). The X-Ray fraction patterns suggested that, in the composite samples, the two matters of MnxZn1-xFe2O4 and a-Fe2O3 existed in its own phase and there is no new matter exist, no reaction between them at all; the composite samples belong to nanometer composite. Furthermore, doping the same powders of a-Fe2O3 (crystal size is about 30 nm ) into different Mn0.40Zn0.60Fe2O4 powders, which were heat treated at different temperature (873 K, 1073 K, 1273 K), the composite pellet samples were gained after sintering at the same condition. We found that, in the composite samples, the crystal size of a-Fe2O3has distinct difference (34.30 nm, 36.20 nm, 47.80 nm) results from the positive different crystal size of MnxZn1-xFe2O4 (68.30 nm,36.20 nm, 114.60 nm). It needs further study about the physical mechanism.(3). We studied the properties of (MnxZn1-xFe2O4)1-y/(a-Fe2O3)y composite with the changeof a-Fe2O3 contents ingredient and preparation conditions. The heuristic results are as follows: (1) After doping appropriate... |
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