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研究生： 廖哲敬
Liao, Che-Ching
論文名稱： 鈣摻雜之鈦酸鋇陶瓷體電阻衰退行為與交流阻抗分析之關係
Relationship between Resistance Degradation and Impedance Spectroscopy of Ca-Doped Barium Titanate
指導教授： 黃啟原
Haung, Chi-Yuen
學位類別： 碩士
Master
系所名稱： 工學院 - 資源工程學系
Department of Resources Engineering
論文出版年： 2017
畢業學年度： 105
語文別： 中文
論文頁數： 75
中文關鍵詞： 鈦酸鋇 、富鈦 、晶體結構 、顯微結構 、電阻衰退 、阻抗分析
外文關鍵詞： Barium Titanate, resistance degradation, impedance spectroscopy
相關次數： 點閱：134  下載：18 
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    • 本研究經收集前人文獻後知，可藉由鈣摻雜到鈦酸鋇陶瓷體中，能夠改善
    陶瓷體的電阻衰退行為。但 Ca2+ 會同時取代鈣鈦礦結構中的 A-site 以及 Bsite；當 Ca2+ 取代 B-site 時，會形成 acceptor 反而使陶瓷體的電阻衰退行為 惡化。為確保 Ca2+ 取代A-site，故額外添加 0.5 mol% 的 TiO2，以促使 Ca2+ 取代 B-site 進行等價取代，進而提升陶瓷體的可靠度。 實驗結果顯示，將 (Ba1-xCax)Ti1.005O3 (x= 0、0.04、0.08 及 0.12) 單一相粉末，以 Rietveld 方法模擬精算結構因子，可以發現，鈣的添加量上升會導致晶 格體積縮小，但正方性無顯著變化，此行為符合Ca2+ 取代 Ba2+ 之行為；且從 高速壽命測試實驗中證實了 Ca2+ 的確提升了陶瓷體的可靠度，也可藉此證明 在本實驗中 Ca2+ 的確是進入 A-site 而非 B-site 。為了模擬積層陶瓷電容器 之燒結條件，故於還原氣氛 (1% H2/N2) 下燒結，故本實驗亦額外添加了 0.5 mol% 的 MnCO3 改善陶瓷體半導化的情況；經燒結後可得到平均粒徑為 0.36 μm 之均勻微結構。從阻抗分析的結果顯示，當添加 Ca2+ 後使得陶瓷體的晶粒 和晶界的導電率下降，這是由於 Ca2+ 摻雜使還原焓上升，讓氧空缺濃度下降， 故使得電子濃度也跟著下降，進而提升陶瓷體的可靠度。而其導電活化能、空 乏層厚度、晶界能障高度則呈現變化不大的結果，這是由於添加了相同濃度的 MnCO3 作為 acceptor 所導致。故在相同製程下，若想分析導電率活化能、空 乏層厚度、晶界能障高度和陶瓷體電阻衰退行為之關係，必須添加不同濃度的 acceptor 方能解析。

    The objective of this study was to find the relationship between resistance degradation and impedance spectroscopy. The A/B ratio of (Ba1-xCax)Ti1.005O3¬ (x= 0、0.04、0.08 and 0.12) was set for Ti-excess to prevent Ca doping onto the B-site. Powder of (Ba1-xCax)Ti1.005O3¬ was calcined at 1050°C which temperature can make the powder no second phase. To simulating the MLCC sintering condition, the BT and BCT ceramics should be sintered in reduction atmosphere to prevent the Ni electrode oxidation, and we also add the 0.5 mol% MnCO3 to prevent the ceramic samples semiconduction. The grain sizes approximately 0.35 μm which fits the MLCC condition. We use two RQ equivalent circuit model to fit the impedance spectroscopy data, and the results meet the Curie-Weiss behavior. According to the resistance degradation data, we can know that Ca-doped could improve the ceramic reliability. All Ca-doped BaTiO3 (BCT) samples have lower grain and grain boundary conductivity than that of pure BT and this is the reason why BCT have better reliability than pure BT, while the depletion layer and grain boundary barrier height are the same in the BT and BCT samples.

    目錄 摘要 I 致謝 XIV 表目錄 XVIII 圖目錄 XIX 第一章 緒論 1 1-1 前言 1 1-2 研究目的 2 第二章 文獻回顧與理論基礎 3 2-1 鈦酸鋇介電材料 3 2-1-1 鈦酸鋇之晶體結構及性質 3 2-1-2 鋇鈦比對於鈦酸鋇之影響 6 2-2 Ca2+添加對鈦酸鋇的影響 9 2-3 鈦酸鋇半導化現象及改善 12 2-4 電性分析 13 2-4-1 交流阻抗分析 13 2-4-2 Electric Modulus分析 22 2-4-3 等效電路的設計 25 2-4-4 陶瓷體導電率分析 25 第三章 實驗方法及步驟 28 3-1 粉末製備及分析 28 3-1-1 起始原料 28 3-1-2 鈣摻雜鈦酸鋇粉末製備 29 3-1-3 粉末之熱差/熱重分析 29 3-1-4 X光繞射儀 30 3-2 陶瓷體製備及分析 31 3-2-1 陶瓷體製備 31 3-2-2 陶瓷體密度量測 31 3-2-3 掃描式電子顯微鏡與微結構觀察及分析 32 3-3 電性量測 33 3-3-1 陶瓷體電性量測樣品準備 33 3-3-2 交流阻抗分析樣品準備及量測 33 第四章 結果與討論 34 4-1 起始混合粉末之DTA/TG 分析 34 4-2 煅燒粉末分析 36 4-2-1 結晶相分析 36 4-2-2晶體結構分析 39 4-3 燒結體分析 45 4-3-1 燒結收縮曲線量測 45 4-3-2 燒結體密度量測 47 4-3-3顯微結構分析 48 4-4 高速壽命試驗分析 52 4-5 交流阻抗分析 54 4-5-1 設計等效電路 54 4-5-2 Curie-Weiss行為分析 59 4-5-3導電率行為分析 62 4-5-4空乏層(空間電荷層)分析 65 4-5-5晶界能障高度分析 67 第五章 結論 70 參考文獻 72 表目錄 Table 3-1 Brands and purity of reagent-grade starting powders. 29 Table 3-2 The operation condition of X-ray powder diffractometer 30 Table 4-1 Results of Rietveld method of (Ba1-xCax)Ti1.005O3 powder. 41 Table 4-2 Relative densities of (Ba1-xCax)Ti1.005O3 bulks sintered at various temperature. 47 圖目錄 Fig. 2-1 The crystal structure of BaTiO3. [4] 4 Fig. 2-2 Displacement of Ti in crystal structure of BaTiO3. [5] 4 Fig. 2-3 The variation of dielectric constant versus temperature and crystal structure of BaTiO3……………………………………………………………………….5 Fig. 2-4 Pseudo-binary phase diagram of the BaO–TiO2 system under ambient air conditions.[9]. 7 Fig. 2-5 Optical micrographs of samples sintered at 1350°C exhibiting the effects of the Ba/Ti ratio on microstructure : (a) Ba/Ti=0.97, (b)Ba/Ti=0.99, (c) Ba/Ti=1, (d) Ba/Ti=1.01, (e) Ba/Ti=1.03.[15] 8 Fig. 2-6 Lattice parameters (a) and volume (b) as a function of Ca concentration in Ba1-xCax+yTi1-yO3-y(x>>y and x<<y) compositions, which are originally designed to be 100% Ba-site occupancy (y=0) and 100% Ti-site occupancy (x=0). [17] 100 Fig. 2 7 Lattice volume and tetragonality (c/a) change of perovskite structure in calcined (Ba1-xCax)mTiO3 powders.[18] 111 Fig. 2 8 Time dependence of the resistance under the accelerated life tests for BaTi1.003O3 and (Ba0.94Ca0.06)1.003TiO3. [18] 111 Fig. 2 9 Impedance response for equivalent circuits of (a) R and (b) C element. 16 Fig. 2-10 Impedance response for equivalent circuits of one series RC element. 18 Fig. 2-11 Impedance response for equivalent circuits of one parallel RC element. 18 Fig. 2-12 Impedance response for equivalent circuits arranged in parallel. 21 Fig. 2-13 Complex impedance for R1 = 108 Ω, R2 = 106 Ω, C1 = C2 = 10-12 F[25] 24 Fig. 2-14 Impedance Z” and modulus M” spectroscopic plots against frequency ω = 2πf for the circuit shown[25] 24 Fig. 2-15 Simulated GB concentration profiles of the mobile charge carriers oxygen vacancies (Vo) holes ( p ) and electrons ( n )[28] 27 Fig. 2-16 Simulation of the partial conductivities of electrons (σn), holes (σp), and oxygen vacancies (σvO) for 0.2 at. % acceptor- Ni- doped SrTiO3[29] 27 Fig.3-1 Flowchart of sample preparation, material characterization, and properties measurement 28 Fig. 4-1 The DTA/TG curves of BaO and TiO2 raw powder (BaTi1.005O3). 35 Fig. 4-2 The XRD patterns of (Ba1-xCax)Ti1.005O3 powder calcined at 1000°C 37 Fig. 4-3 The XRD patterns of (Ba1-xCax)Ti1.005O3 powder calcined at 1050°C 37 Fig. 4-4 The XRD patterns of (Ba1-xCax)Ti1.005O3 powder calcined at 1100°C 38 Fig. 4-5 The Rietveld method fitting of (Ba1-xCax)Ti1.005O3 (x=0) 42 Fig. 4-6 The Rietveld method fitting of (Ba1-xCax)Ti1.005O3 (x=0.04) 42 Fig. 4-7 The Rietveld method fitting of (Ba1-xCax)Ti1.005O3 (x=0.08) 43 Fig. 4-8 The Rietveld method fitting of (Ba1-xCax)Ti1.005O3 (x=0.12) 43 Fig. 4-9 Lattice volume change of ( Ba1-xCax )Ti1.005O3 ( x = 0-0.12) 44 Fig. 4-10 The tetragonality of (Ba1-xCax)Ti1.005O3 (x=0-0.12) 44 Fig. 4-11 Shrinkage curves of (Ba1-xCax)Ti1.005O3 samples 46 Fig. 4-12 Shrinkage rate curves of (Ba1-xCax)Ti1.005O3 samples 46 Fig. 4-13 SEM micrograph of (Ba1-xCax)Ti1.005O3 bulk sintered at 1230°C /1 h (sintered in MLCC condition). 49 Fig. 4-14 SEM micrograph of (Ba1-xCax)Ti1.005O3 bulk sintered at 1200°C /1 h (sintered in MLCC condition)………………………………………………...51 Fig. 4-15 Grain size distribution of (Ba1-xCax)Ti1.005O3 with different sintering conditions (sintered in MLCC condition).x = 0、0.04、0.08 samples were sintered in 1230°C /1 h and x = 0.12 sample was sintered at 1200°C /1 h. 51 Fig. 4-16 Electrical resistivity at high temperature (160°C) versus voltage (1400 V/mm) for (Ba1-xCax)Ti1.005O3 (x = 0-0.12) ceramics sintered in reducing atmosphere 53 Fig. 4-17 A sketch of the brick wall model and the equivalent circuit model.[28] 54 Fig. 4-18 Complex impedance plane plots of measured (solid circle) and fitted (red line) data for (Ba1-xCax)Ti1.005O3 ceramics (x = 0-0.12) recorded at 260°C (sintered in MLCC condition) 56 Fig. 4-19 Impedance Z” and modulus M” spectroscopic plots against frequency recored at 260°C for (Ba1-xCax)Ti1.005O3 ( x = 0-0.12) ceramics sintered at 1200°C and 1230°C for 1h in reducing atmosphere 57 Fig. 4-20 Electric modulus M” spectroscopic plots against frequency for(Ba1-xCax)Ti1.005O3 ( x = 0-0.12) ceramics sintered at 1200°C and 1230°C for 1 h in reducing atmosphere 58 Fig. 4-21 Reciprocal values of (a) grain and (b) grain boundary capacitance versus temperature of (Ba1-xCax)Ti1.005O3 ceramics (sintered in MLCC condition). 61 Fig. 4-22 (a) Grain and (b) grain boundary conductivity versus reciprocal temperature of (Ba1-xCax)Ti1.005O3 ceramics (sintered in MLCC condition). 64 Fig. 4-23 Depletion layer thickness of (Ba1-xCax)Ti1.005O3 ceramics that obtained from impedance fitting result (sintered in MLCC condition). 66 Fig. 4-24 Potential barrier height that were obtained from fitting of the impedance data for (Ba1-xCax)Ti1.005O3 (x = 0-0.12) ceramics (sintered in reducing atmosphere). 69

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