臺灣博碩士論文加值系統

摘 要
為使尖晶石相的錳鋅鐵氧磁粉，能使用在高頻變壓器、多層晶片感應器(multilayer chip inductor，需與銀內電極共燒，銀的熔點≒962℃)、及高速讀/寫磁頭的應用(需具備高緻密性、低孔隙率之燒結體)上，粉末必須具優異的燒結活性，低溫燒結緻密的特性。本研究即以此為目的，以水熱處理法調製超微粒錳鋅鐵氧磁粉。
本研究選用Fe2O3：MnO：ZnO = 70.85：20.4：8.75 (wt %) = 52.9：34.3：12.8 (mol %)為合成錳鋅鐵氧磁粉之目標組成配比。實驗是將硝酸鐵、硝酸錳及硝酸鋅等金屬硝酸鹽溶液，依目標組成之化學劑量比混合；之後，於攪拌狀態下將所需之氨水，依R值(鹼性度，alkalinity) = (moles of added OH-) / [(moles of added Fe3+)×3 + (moles of added Mn2+) + (moles of added Zn2+)×2]，加入反應容器中(本實驗控制R值 = 2∼6)，再於150℃下水熱處理2∼16 h。實驗是檢討水熱製程參數如R值(alkalinity)、水熱處理時間等，對合成粉末之特性及燒結性之影響。
實驗結果顯示：在粉末特性方面，混合溶液的R值與水熱處理時間對合成粉末之組成、結晶子大小、錳鋅鐵氧磁體之尖晶石相比例及結構等，具有決定性之影響。當R值增大時，合成粉末中的結晶粒子大小亦增大，尖晶石相比例減少，而粉末中α-Fe2O3的量增多；水熱處理時間≧8 h時，水熱反應(包括化學反應與粒子成長)已趨於穩定。R值愈大時，水熱處理過程中鋅離子的損失量會愈多，使合成的(MnxZn1-x)O．Fe2O3尖晶石結構中之Mn/Zn比例增大。針對鋅離子的損失，本實驗藉由添加適量鋅離子於起始溶液中，則可合成所欲組成之磁粉。水熱合成之錳鋅鐵氧磁粉，其粒徑甚小，15∼25 nm；在氮氣氣氛中900或950℃下燒結2 h，所得燒結體之相對密度達95∼99 %。
在燒結體性質方面，磁性質的表現亦與R值(影響燒結體的成份組成、粒徑大小等)有關。當R值增加時，Bs、Br及mi值減少，而Hc值增加。本研究藉由多添加鋅離子於起始溶液中的補償方式，除了可以得到所欲組成之錳鋅鐵氧磁粉外，其燒結體之Bs值及mi值亦獲得改善，且不會降低其燒結密度。

Abstract
For the application of power transformers, multilayer chip inductor that co-heated with silver internal electrodes (Tm≒965℃), and read/write heads of high-speed magnetic recording which require high density and low-porosity, the Mn-Zn ferrite powders have to exhibit excellent sinterability and the characteristic of low-temperature sintering. For the purpose of the mentioned, ultrafine Mn-Zn ferrite powders were prepared by the hydrothermal synthesis in this study.
The expected composition of the Mn-Zn ferrite powder is Fe2O3：MnO：ZnO = 70.85：20.4：8.75 (wt %) = 52.9：34.3：12.8 (mol %). A given quantity of Fe-, Mn-, and Zn-nitrate solutions were mixed, and diluted aqueous ammonia was then added slowly under stirring. The R value (alkalinity) = (moles of added OH-) / [(moles of added Fe3+)×3 + (moles of added Mn2+) + (moles of added Zn2+)×2] was introduced to adjust the amount of added ammonia (R = 2∼6). The time of hydrothermal synthesis was between 2 h and 16 h and the synthesized temperature is 150℃. The effects of R value and hydrothermal time etc. on the powder characterization of synthesized Mn-Zn ferrite and its sinterability. were investigated.
I. For the powder characterization, the results show that： the R value of starting suspension and the hydrothermal time have dominant effects on the composition, crystallite size, spinel ratio and structure of synthesized Mn-Zn ferrite powders. As R value of the starting suspension increases, the crystallite size increases, spinel ratio decreases, and the more amount of α-Fe2O3 existing in synthesized powders. The hydrothermal reactions (including chemical reaction and particle growth) nearly come to balance as hydrothermal time≧8 h. While R value increases, the loss of Zn ion increases during hydrothermal process, so that the Mn/Zn ratio in spinel structure ((MnxZn1-x)O．Fe2O3) increases. According to the loss of Zn ion during hydrothermal process, the expected composition of Mn-Zn ferrite powder was obtained by adding appropriate amount of zinc nitrate in the starting suspension. The crystallite size of synthesized powders are so small, 15∼25 nm, that high densities, 95∼99 % of theoretical densities, have been obtained upon sintering green ferrite powders at relatively low temperature, 900 or 950℃, in N2 atmosphere.
II. For the characteristics of sintered bodies, the results show that：the R value affects the composition, grain size and the magnetic properties of sintered body. As R value increases, the Bs, Br, and mi values decrease, but the Hc value increases. In this study, not only the expected composition of Mn-Zn ferrite is obtained but also the Bs and mi values of sintered body without lowing down the relative sintered density is improved by adding more amount of Zn ion in the starting suspension.

目 錄
中文摘要***********************.I
英文摘要**********************..III
目錄************************..V
表目錄**********************..VIII
圖目錄***********************..X
第一章 緒論*********************1
1-1 前言********************1
1-2 研究目地******************2
第二章 理論基礎與前人研究**************4
2-1 磁性理論******************4
2-1-1 磁性的起源***************.4
2-1-2 磁性的分類***************.5
2-1-3 磁性質基本理論*************8
2-2 尖晶石型鐵氧磁體**************..9
2-3 水熱合成法*****************.10
2-3-1 水熱法的原理*************..10
2-3-2 水熱法製備粉體的優點*********12
2-3-3 水熱製程的改進************12
2-4 燒結理論******************.13
第三章 實驗步驟與方法***************27
3-1 實驗流程******************.27
3-2 粉體之製備及燒結**************.28
3-2-1 起始原料***************28
3-2-2 混合*****************28
3-2-3 水熱處理***************28
3-2-4 離心、乾燥***************29
3-2-5 成形*****************29
3-2-6 燒結*****************29
3-3 性質分析及觀察方法*************.30
3-3-1 成份分析..***************30
3-3-2 結晶相及錳鋅鐵氧磁體之尖晶石相比例分析..30
3-3-3 粒子形態及結晶粒子大小分析******30
3-3-4 紅外線吸收光譜分析**********31
3-3-5 熱差/熱重分析*************31
3-3-6 熱膨脹收縮分析************32
3-3-7 微結構觀察及分析***********32
3-3-8 燒結體密度分析************32
3-3-9 磁性質分析**************33
第四章 結果與討論*****************..41
I. 粉體特性*******************..41
4-1 合成粉末之相分析**************.41
4-1-1 粒子形態及結晶相***********..41
4-1-2 鹼性度(alkalinity, R值)及水熱處理時間的影
響******************..41
4-2 合成粉末之成份組成*************.42
4-2-1 水熱處理條件對尖晶石相中Mn/Zn比例之
影響*****************.42
4-2-2 Mn2+離子及Zn2+離子在水熱處理中的損失量..44
4-3 尖晶石相比例及結晶粒子大小*********.45
4-4 ZnO成份量之修正**************..46
4-5 粉體表面特性**.**************47
4-6 熱差/熱重分析****************48
4-6-1 空氣氣氛中分析************..48
4-6-2 氮氣氣氛中分析************..49
4-6-3 煆燒對合成粉體之影響*********..50
4-7 綜合討論******************.50
II. 燒結體性質**.****************74
4-8 相分析*******************.74
4-9 燒結收縮曲線****************.74
4-10 合成粉末之燒結性*************..75
4-11 微結構分析****************..77
4-12 磁性質******************78
第五章 結論********************90
參考文獻**********************..91

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