燃燒法製備鐵氧磁體與其電磁特性研究

Electromagnetic Characterization of Mn-Zn/Ni-Zn Ferrites Fabricated by Combustion Method

薛銘儒(Ming-Ru Syue)

指導教授 ： 周傳心

共同指導教授 ： 傅昭銘(Chao-Ming Fu)

國立臺灣大學/工學院/應用力學研究所/博士(2011年)

https://doi.org/10.6342/NTU.2011.10442

摘要

本研究旨在探討以節能為目的之鐵氧磁體製程。尖晶石結構的鐵氧磁體具有高導磁率和低磁滯損失等優異的特性，是極為廣泛應用的電磁材料。雖然近年來已有化學共沉法、水熱反應法、噴霧熱解法等數種化學合成法，用來製作電磁特性良好的鐵氧體，但是複雜的製程、昂貴的材料、和極低的生產量，是使用化學方法普遍存在的問題。此外，有些傳統的燃燒法在相對低的反應溫度和較短的反應時間內製備鐵氧體，但是要得到良好的晶相結構與良好的電磁特性，仍須要進行長時間的高溫熱處理。有鑑於此，本文發展不須熱處理的新式燃燒法，以製備良好性質的鐵氧體，並探討由此法製備的鐵氧體其微結構與電磁特性。
以X射線繞射儀和掃描式電子顯微鏡，了解合成材料的微結構和表面形貌。此法燒結後的鐵氧體經由X射線繞射儀分析，均得到具有單純晶相結構。掃描式電子顯微鏡的結果顯示，材料顆粒均質性佳，且大小一致。振動樣品測磁儀量測錳鋅和鎳鋅鐵氧體材料之磁特性。本文針對飽和磁化強度、矯頑磁力、導磁係數等磁特性，與材料的組成比例的相關性進行系統化的分析。此外，藉由等效電路模型解釋複數阻抗頻譜，分析材料高頻電磁特性並探討其介電機制。
綜言之，本文發展不須後續熱處理的新式燃燒法，因具備相對高效率、高品質和低成本等特色，可應用於產業合成與高頻元件製備。

關鍵字

燃燒法 ； 奈米磁顆粒 ； 鐵氧體 ； 尖晶石 ； 阻抗 ； 介電

並列摘要

Spinel ferrites, such as Mn–Zn or Ni–Zn ferrites, are of interest for their high initial permeability and low hysteresis loss. Several chemical methods to prepare high electromagnetic performance ferrites, such as chemical coprecipitation, hydrothermal reactions, and aerosol pyrolysis, have been developed recently. However, complex processes, expensive precursors, and low production rates are common problems in wet chemical methods mentioned above. On the other hand, even though ferrite powders can be formed at lower temperature or in shorter time by several of the reported combustion techniques, high temperature and long-time heat-treatment processes are still necessary for the pure crystalline phase and high electromagnetic performance. Consequently, a novel combustion route without sequential heat treatment to synthesize nanocrystalline ferrites was studied. The electromagnetic and the micro-structural properties of as-synthesized ferrites were also investigated.
The microstructure and morphology were characterized by X-ray diffraction and scanning electron microscopy, respectively. The sintered ferrites characterized by X-ray diffraction have shown highly pure nanocrystalline phase. Moreover, SEM micrographs of the synthesized ferrite showed that most of the ferrite particles were fine, homogeneous with narrow particle distributions.
The magnetic properties were measured using vibrating sample magnetometer. The dependence between the content and the magnetic properties, such as the permittivity, saturated magnetization and coercivity, was analyzed systematically. Further, the analysis of complex impedance spectra by an equivalent circuit model was used to explain the AC electrical conduction mechanism.
In brief, the results imply that this novel combustion method without further thermal treatment is relatively efficient and economical as compared to conventional methods for industrial synthesis of nano-sized ferrites in high frequency electromagnetic devices applications.

並列關鍵字

combustion method ； nanoparticle ； ferrite ； spinel ； complex impedance ； dielectric properties

參考文獻

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