| Summary: | 碩士 === 國立臺灣大學 === 應用力學研究所 === 97 === Polycrystalline ferrites, due to their versatile magnetic and electrical behaviors, have many applications, such as high frequency transformer and recording heads etc. There are many synthesis methods of ferrite material, including conventional solid solution method, coprecipitation, sol-gel, hydrothermal, citrate precursor, etc. In recent years, there has been tremendous interest in utilizing the combustion synthesis for ultra-fine powders of polycrystalline ferrites. In the most of reported combustion methods for ferrites, post annealing processes are required to improve the phase purity and magnetic properties of ferrites. It is of interest to improve synthesis condition of combustion in order to prevent the post annealing process, for not only the energy saving but efficiency of process.
In this thesis, novel synthesis conditions to improve the combustion synthesis for ferrites have been investigated. In the course of this study, ferrites were synthesized utilizing combustion reaction with various processing parameters. The synthesized ferrites were characterized by X-ray diffraction and scanning electronic microscopy. Magnetic properties were measured using vibrating sample magnetometer and magneto-impedance properties were measured using impedance analyzer. The results have demonstrated the ferrites synthesized by combustion method without post annealing process are highly purity phase, with an average grain size about 20 ~ 70 (nm) estimated using Scherrer’s formula, the saturated magnetization are in the range of 5 ~ 62 (emu/g) and coercivity varies about 10 ~ 200 (Oe).
The synthesized ferrites with highly purity phase can be applicable for high frequency electromagnetic devices. Details will be discussed in the thesis.
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