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研究生： 梁育瑋
Liang, Yu-Wei
論文名稱： 鈣鈦礦 LaCo(1-x)Nb(x)O3 之電性研究及介電特性探討
The Dielectric and Electrical Study on Perovskite LaCo(1-x)Nb(x)O3
指導教授： 張炎輝
Chang, Yen-Hui
學位類別： 碩士
Master
系所名稱： 工學院 - 材料科學及工程學系
Department of Materials Science and Engineering
論文出版年： 2005
畢業學年度： 93
語文別： 中文
論文頁數： 70
中文關鍵詞： 介電性質 、鑭 、鈣鈦礦
外文關鍵詞： perovskite, dielectric properties, lanthanum
相關次數： 點閱：128  下載：3 
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    • 　　本實驗是利用固相反應法製備LaCo(1-x)Nb(x)O3，根據結晶化學理論選擇Nb取代部分的Co原子以形成LaCo(1-x)Nb(x)O3固溶體。藉由基本的結構分析以及介電、電性分析、研究Nb的添加對結構以及電性之影響。

    　　實驗結果顯示Nb在LaCo(1-x)Nb(x)O3中固溶度大約在5 at.％，會隨著添加量的增加會使得密度變小、孔隙率增大，且又具有細化晶粒的作用。LaCo(1-x)Nb(x)O3受空間極化機制的影響極大，發現添加1at.％的Nb會增加LaCo(1-x)Nb(x)O3的介電常數，此時在外加頻率為1KHz的時具有最大的介電常數值為12878，但隨著Nb含量之增加反而會因為孔隙率增加致使介電常數大幅下降。此即由於Nb離子半徑較大而縮短了八面體層間的距離，因此加強了層間的作用力，所以居理溫度會朝高溫移動。藉由電阻量測知道LaCo(1-x)Nb(x)O3具有NTCR效應。

    　The LaCo(1-x)Nb(x)O3 solid solution was prepared by solid state reaction . According to the crystal chemistry theory, Nb5+ was doped into the LaCoO3 with perovskite structure. Solid soulution was synthesized by Nb5+ substituting for part site of Co3+ . The structure and electrical properties for Nb doped LaCo(1-x)Nb(x)O3 was investigated by basic structure analysis, dielectric and electrical behavior.

    　Experimental result show that the solubility of Nb in LaCoO3 is about 0.05 , There are severely decrease in density but increase in porosity as Nb increased , it also reveals that the Nb addition is favor to inhibit the grain growth of matrix. The highest dielectric constant is LaCo0.99Nb0.01O3, the relative dielectric constant is 12878 at the frequency 1KHz . But porosity increased and the density decreased with increasing the amount of Nb ions, the dielectric constant also decreased with increasing the amount of Nb ions.The distance between octahedron layer decreased because the Nb ion was larger than Co ions , therefore , the Curie temperature shift to higher temperature .

    中文摘要...................................................I Abstract..................................................II 目錄.....................................................III 圖目錄....................................................VI 表目錄....................................................VI 第一章 前言................................................1 1-1簡介..................................................1 1-2研究動機..............................................3 第二章 基礎理論與文獻回顧..................................4 2-1 鈣鈦礦結構 (Perovskite structure)....................4 2-2 導電性..............................................11 2-2-1 導體機制........................................11 2-2-2 半導體機制......................................13 2-3 電阻之溫度係數......................................14 2-4 介電理論............................................18 2-4-1介電性質.........................................18 2-4-2 極化機制........................................18 2-4-3 介電特性參數....................................20 2-5 置換作用............................................24 2-5-1 置換原理........................................24 2-5-2 異價取代機制以及缺陷化學式......................24 第三章 實驗方法及步驟.....................................26 3-1 實驗流程圖..........................................26 3-2 粉末製備............................................27 3-3 塊材製備............................................27 3-4 晶體結構分析........................................28 3-4-1 XRD結構分析.....................................28 3-4-2 塊材成分分析....................................29 3-4-3 孔隙率、密度測量................................29 3-4-4 掃描式電子顯微鏡 SEM 分析.......................30 3-5 性質量測............................................30 3-5-1 介電性質(Dielectric Properties)之量測...........30 3-5-2 電阻溫度係數的量測..............................31 第四章 結果與討論.........................................32 4-1 XRD繞射分析.........................................32 4-1-1 粉末XRD繞射分析.................................32 4-1-2 塊材XRD繞射分析.................................41 4-2 EDS成分分析.........................................41 4-3 塊材密度及孔隙率....................................44 4-4 掃描電子顯微鏡SEM分析...............................47 4-5 電性量測............................................52 4-5-1 介電性質分析....................................52 4-5-2 電阻性質量測....................................62 第五章 結論...............................................67 參考文獻..................................................69

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