臺灣博碩士論文加值系統

在本研究中，利用傳統之固態反應法，添加氧化譜(Pr6O11)及氧化鈷(Co3O4)於氧化鋅(ZnO)變阻器中。為了降低燒結溫度，則以添加微量之碳酸鈉(Na2CO3)燒結助劑幫助燒結。本研究主要探討燒結助劑，燒結溫度，冷卻方式對Pr6O11-ZnO陶瓷體變阻特性之影響。研究中以X光繞射儀(XRD)鑑定以及計算PrOx之結晶相之量、以場發射電子顯微鏡(FESEM)觀察胚體之顯微組織、以電子微探儀(EPMA)了解Pr以及Na之分佈，以了解這些因素對ZnO變阻器變阻特性之影響。
實驗結果顯示，當胚體中PrOx結晶量較多時，變阻特性較佳。添加微量的Na2CO3有助於變阻特性之提升。當冷卻速率較慢時，由於可增加氧在晶界上擴散的時間，有助於Pr及Co以高價存在，由於過渡金屬Co若在高價態取代Zn之位置，將產生鋅空缺，而有助於氧之化學吸附，形成界面陷阱，而提升變阻特性；而在冷卻速率越快時，PrOx則會富集在triple point，導致變阻特性變差。
整體而言，製程條件為添加Na2CO3、燒結溫度：1200oC、冷卻速率：2oC/min的樣品具有最佳的變阻特性，其α值為19.6；Eb值為637.6V/mm，IL為285μA。

In this study, ZnO varistor doped with Pr6O11, Co3O4, were prepared using traditional solid-state reaction method. In order to decrease the sintering temperature, trace additive, Na2CO3, was added as a sintering aid. The effects of the additive, sintering temperatures, cooling rate on the microstructures and electrical properties of (Pr,Co,Na)-added ZnO ceramics were investigated using XRD, XPS, FESEM, and EPMA.
The observed results can be described as follows:
1. The samples added Na2CO3 possessed better varistor properties.
2. Better varistor properties can be obtained for the samples with much crystalline PrOx phase.
3. For the sample with a slow cooling rate, O2 had a much time to diffuse at grain boundary which resulted in the more adsorption of O2 on the surfaces of the grains. Therefore the superior varistor properties were obtained for the sample with a slow cooling rate compared to the sample with a rapid cooling rate. For the sample with a rapid cooling rate, PrOx phase was observed to be rich in triple point, which resulted in the degradation of varistor properties.
In conclusion, the Pr-doped ZnO ceramics added with Na2CO3, sintered at 1200oC, and at cooling rate of 2oC/min can obtain the best varistor properties: α is 19.6 , Eb is 637.6 V/mm, and IL is 285μA.

摘要.............................................................................................................I
Abstract…………………………………………………………………..II
致謝……………………………………………………………………..III
目錄……………………………………………………………………..IV
表目錄……………………………….………………..………………..VII
圖目錄……………………………….………………..………………VIII
第一章、緒論……………………………………………………………1
1-1 前言………………………………………………..………………..1
1-2 研究目的……………………………………………………..……..2
第二章、前人研究與理論基礎..................................................................3
2.1變阻器…………………………………………………………….…3
2.1.1變阻器之應用..................................................................................3
2.1.2 ZnO-Pr變阻器................................................................................5
2.2 變阻性質之生成機構…………………………………………….13
2.2.1雙重Schottky能障(Double Schottky barrier)…………………..13
2.2.2非歐姆特性(non-Ohmic characteristic)…………………………15
2.3 晶界參數之計算.....………………………………………………19
2.4 變阻係數之關係……...…………………………………………..22
2.4.1 α值與晶界參數…...………………………………………….22
2.4.2 電容與晶粒大小……...……………………………………….22
2.4.3 崩潰電場與晶粒大小及晶界參數…………...……………….22
2.4.4 影響崩潰電場之因子……………...………………………….22
2.5 過渡金屬離子…………………...………………………………..24
2.6 冷卻速率對變阻性質之影響………………...…………………..26
2.7低溫燒結 ………………...………………………………………..27
第三章、實驗步驟 ..................................................................................28
3.1 實驗原料………………………………………………………….28
3.2 實驗架構………………………………………………………….29
3.3 實驗流程………………………………………………………….30
3.3.1 粉末的製備……………………………………………………31
3.3.2 胚體成形，燒結……………………………………………….32
3.3.3 特性分析………..……………………………………………..32
3.3.3.1 變阻特性分析.......................................................................32
3.3.3.2 結晶相分析………………………………………………...32
3.3.3.3 燒結密度分析……………………………………………...32
3.3.3.4 金相觀察…………………………………………………...33
3.3.3.5 XPS量測………..………………………………………...33
第四章、結果與討論................................................................................34
4.1 燒結體性質.………………………………………………………34
4.2 變阻性質………………………………………………………….53
第五章、結論……………………………………………………………63
參考文獻………………………………………………………………64
附錄……………………………………………………………………68

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