Electromagnetic Properties of Nanosized MnZn/NiZn Ferrites Synthesized by Combustion Method

鐵氧體材料具有特殊的介電與磁特性且被廣範應用於日常生活，例如高功率電源轉換器、磁讀寫及電磁吸收體等。鐵氧體材料的製程方式包含了固態法、共沉法、溶膠-凝膠法、水熱法，以及近幾年由Patil等人所發表之火燄燃燒法。根據文獻，火燄燃燒法所備製的鐵氧體材料仍須經由長時間的高溫熱處理以去除反應不完全的雜相。而高溫熱處理過程所需的能量及時間，相對地提高了材料備製的成本。因此，若能夠省去高溫熱處理的步驟，必將提高材料製程的效率並且降低製程成本。本實驗透過改變火燄燃燒法的製程參數，備製鐵氧體材料。將未經高溫熱處理的樣品，經由X光粉末繞射儀及掃描式電子顯微鏡觀察其結晶特性，並利用振盪樣品磁度儀及阻抗分析儀量測樣品的磁電特性。經由實驗結果得知，透過特定的製程參數，可在不經高溫熱處理的前提下，備製高純相的鐵氧體材料，且其磁特性亦明顯提升。透過本實驗所改進的火燄燃燒法，可備製高純相及良好磁特性的鐵氧體材料，且因不須經由高溫熱處理，大幅提升了材料製程效率。關於材料特性的量測及分析，將在本論文中進一步討論。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.n 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). he synthesized ferrites with highly purity phase can be applicable for high frequency electromagnetic devices. Details will be discussed in the thesis.口試委員審定書 Acknowledge IIcknowledge III要 IVbstract Vable of Content VIist of Figures VIIIist of Tables XIIhapter 1 Overview 1-1 Magnetic Material and Spinel Ferrites Background 1-2 Combustion Synthesis Background 3-3 Structure of This Thesis 4hapter 2 Theory 5-1 Magnetic Properties 5-2 Classification of magnetic material 7-2.1 Diamagnetism 7-2.2 Paramagnetism 8-2.3 Antiferromagnetism 9-2.4 Ferromagnetism 10-2.5 Ferrimagnetism 11-3 Hysteresis Loop 14-4 Spinel Structure 20-5 Model of Cation distribution in the Oxide Spinels 32hapter 3 Experimental Procedures 39-1 Preparation of Sample 41-2 Experimental Measurement 42-2.1 X-ray Diffraction (XRD) 42hapter 4 Experimental results 48-1 Combustion Synthesis with Different Volume of Solvent 48-1.1 Phase Identification 49-1.2 Cation Distribution 52-1.3 Magnetic Properties 57-1.4 Time of Reaction 60-1.5 Data of Processing Parameters and Experimental Result 61-2 Combustion Synthesis with Different Amount of Reducer 62-2.1 Phase Identification 63-2.2 Cation Distribution 67-2.3 Magnetic Properties 71-2.4 Data of Processing Parameters and Experimental Result 76-3 Nickel Ferrite Doped by Zinc 77-3.1 Phase Identification 77-3.2 Cation Distribution 80-3.3 Magnetic Properties 87-3.4 AC Electromagnetic Properties 94-3.5 Processing Parameters and Experimental Data 103-4 Manganese Ferrite Doped by Zinc 104-4.1 Phase Identification 104-4.2 Cation Distribution 107-4.3 Magnetic Properties 114-4.4 AC Electromagnetic Properties 119-4.5 Processing Parameters and Experimental Data 124onclusion 125 eference 12