臺灣博碩士論文加值系統

摘要

　　隨著國際環保意識的提高，使得許多含有對於環境及人體健康有疑慮的元素及材料已被漸漸被禁止使用，而對於壓電陶瓷材料來說，也必定會朝開發出更優良的無鉛壓電材料的方向去努力。
　　(Na1-xKx)NbO3 為目前無鉛壓電材料中較具有潛力的材料系統，其中以 x = 50 atom%, ((Na0.5K0.5)NbO3), 成分的電性質表現最為優良，故本研究利用固態反應法以 complex 的方式同時添加 Sr2+ 和 Zr4+ 兩種異價離子至此成分中，以合成出 (1-x) (Na0.5K0.5)NbO3 - x SrZrO3 固溶系統。針對此系統做詳盡的晶體結構以及基本電性質的分析，並藉由成分改變所產生的晶體結構和電性質變化，進而探討晶體結構和電性質間的關連性及應用為壓電材料的可能性。
　　經實驗結果可以確定以下幾點，第一，合成出 (1-x) (Na0.5K0.5)NbO3 - x SrZrO3 固溶系統，並提升 x = 30 atom% 內各個成分之燒結相對密度達 94% 以上。第二，詳盡說明本系統隨著成分變動使其相變化的過程，於添加量 x = 2.5 atom% 時經過一形變相界 (MPB)，由 Orthorhombic 轉變至 Hexagonal，且經由計算得到其晶格常數、晶格體積及理論密度值。並經由 Rietveld 方法得到晶體結構中各離子間的相對偏移量。第三，得到一系列成分於不同頻率下的介電常數，並提出影響本系統電性質表現的主要因素為晶體結構中 B-site 陽離子相對於 X-site 陰離子的偏移量及晶格常數 c/a 值。第四，確定此固溶系統具有壓電性。

Abstract

　　With the raising of the environmental sense, some materials which contain harmful health elements will be inhibited. For the piezoelectric materials, new lead-free piezoelectric materials with better electric properties will also be developed.
　　(Na1-xKx)NbO3 is a excellent candidate system in lead-free piezoelectric materials system at present, when the doping amount (x) up to 50 atom%, (Na0.5K0.5)NbO3.shows the best electric properties in this system. In this research, the Sr2+ and Zr4+ were both doped into this composition system via solid state reaction with complex method to synthesize (1-x) (Na0.5K0.5)NbO3 - x SrZrO3 solid solution system. The crystal structure and electric properties of this system were studied detail. According to the changes of the crystal structure and electric properties which resulted from the composition variation, the relationship between the crystal structure and electric properties, even the possibility of application were also studied further in this research.
　　The result show that: First, (1-x) (Na0.5K0.5)NbO3 - x SrZrO3 solid solution system could be successful synthesized in this research. As the doping amount (x) below to 30 atom%, the relative density of sintered bulks of each composition can achieve 94% or over. Second, the phase transformation with composition variation of this system was showed in detail in this research. The MPB, Orthorhombic to Hexagonal, was found when x = 2.5 atom%. Besides, the cell parameters, cell volume, and theoretical density were also obtained after the cell parameters calculation. And the Rietveld method was adopted to get the relative displacement distances of atoms in the crystal structure. Third, get the dielectric constant of each composition at different frequency and propose the main factors which affect the dielectric properties are the relative displacement distance between B-site cation and X-site anion and c-a ratio. Fourth, confirm this solid solution system has piezoelectric properties.

目錄

中文摘要 Ⅰ
Abstract Ⅱ
誌謝 Ⅳ
目錄 Ⅴ
表目錄 Ⅷ
圖目錄 Ⅸ

第一章 緒論 1
1-1 前言 1
1-2 研究方向及目的 1
第二章 前人研究及理論基礎 4
2-1 晶體結構及電性質 4
2-1-1 KNbO3 (鈮酸鉀) 4
2-1-2 NaNbO3 (鈮酸鈉) 4
2-1-3 (Na1-xKx)NbO3 (鈮酸鉀鈉) 9
2-1-4 鈮酸鉀鈉固溶系統 14
2-1-5 SrZrO3 (鋯酸鍶) 15
2-2 置換作用 15
2-2-1 置換原理 15
2-2-2 容忍因子 17
2-2-3 結構區域圖 19
2-2-4 異價取代機制與缺陷化學式 21
2-3 介電性質 22
2-3-1 極化機制 22
2-3-2 介電特性參數 23
2-4 壓電性質 27
2-4-1 壓電效應 27
2-4-2 壓電特性參數 33
2-4-3 壓電諧振體 36
2-4-4 形變相界 36
2-5 鐵電性質 37
2-5-1 鐵電效應 37
2-5-2 鐵電滯迴曲線 37

第三章 實驗方法與步驟 42
3-1 起始原料 42
3-2 粉末及燒結體製備 42
3-2-1 粉末製備 42
3-2-2 粉末之熱差/熱重分析 44
3-2-3 �y燒條件測試及粉末合成 44
3-2-4 燒結體製備及燒結條件試驗 44
3-3 材料特性分析 47
3-3-1 燒結體密度量測 47
3-3-2 相鑑定 47
3-3-3 晶格常數計算 51
3-3-4 晶體結構分析 52
3-3-5 顯微結構觀察 56
3-3-6 相轉換溫度量測 56
3-4 材料性質量測 56
3-4-1 電性質量測樣品準備 56
3-4-2 介電常數及品質因子量測 57
3-4-3 室溫直流電阻率量測 57
3-4-4 鐵電滯迴曲線量測 58
3-4-5 極化 59
3-4-6 機電耦合因數量測 59

第四章 結果與討論 61
4-1 粉末合成 61
4-1-1 起始混合粉末之熱差/熱重分析 61
4-1-2 �y燒後粉末之 XRD 相鑑定 64
4-1-3 粉末之微結構觀察 70
4-2 燒結 77
4-2-1 燒結試驗及燒結緻密度 78
4-2-2 燒結體之 XRD 相鑑定 81
4-2-3 燒結體之微結構觀察 81
4-3 晶體結構分析 81
4-3-1 晶格常數計算 81
4-3-2 Rietveld 分析 92
4-4 性質量測 98
4-4-1 介電常數及品質因子 102
4-4-2 直流電阻率 103
4-4-3 鐵電滯迴曲線 106
4-4-4 機電耦合因數 106
4-5 綜合討論 109

第五章 結論 113

參考文獻 114
附錄 A 119
附錄 B 130

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