鈦酸鈣摻雜在非鉛鈮酸鈉鉀壓電陶瓷之物理性質與電性研究

Effect of CaTiO3 Addition on Physical and Electrical properties of Na0.52K0.48NbO3 lead-free piezoelectric ceramics

林雍舜(Yung-Shun Lin)

指導教授 ： 曾俊元

國立臺北科技大學/工程學院/材料科學與工程研究所/碩士(2009年)

https://doi.org/10.6841/NTUT.2009.00425

摘要

隨著國際環保意識的提高，許多含鉛對人體健康有危害的元素以及材料已漸漸被禁止使用，所以非鉛壓電材料的開發是未來研究趨勢。
(Na1-xKx)NbO3 (NKN)為目前無鉛壓電材料中具最佳性能的材料系統，其中以 x = 50 atom%之(Na0.5K0.5)NbO3成分有高的機電耦合常數(kp ~ 0.36)與高的相變化溫度(420℃)。為進一步增進其性能，本研究利用固態反應法添加 CaTiO3 (CT) 至此成分中，以合成出 (1-x) (Na0.5K0.5)NbO3 - x CaTiO3 固溶系統。以X光繞射、電子顯微鏡、拉曼光譜、X光光電子能譜探討其成份及微結構，並量測其鐵電、介電、壓電特性。根據實驗結果來做詳盡的晶體結構、相變化、缺陷以及基本電性質的分析，並藉由摻雜CaTiO3成分改變所產生效應進而探討物理性質和電性質間的關連性及實際應用為壓電材料的可能性。分析結果顯示，摻雜CaTiO3有效改善NKN陶瓷緻密度、壓電性與防止水解。重要的結果歸納如下:
第一，成功製備出(1-x)NKN-xCT陶瓷體，其相對密度可達95%以上。於x = 0.03添加量時，其晶粒尺寸約為1 μm具有最佳的晶域轉動能力。在漏電流、XPS與交流阻抗分析結果發現，CT的摻雜會減少電子、電洞缺陷與潮解問題，但是會降低阻抗值。本論文並利用電負度與容忍因子關係來預測新的壓電材料系統MPB區間。第二，隨著CaTiO3摻雜致使NKN產生相變化，於添加量 x = 0.03時經過一形變相界(MPB)與TO-T溫度降低到室溫附近有最佳電性，壓電常數(d33 = 117 pC/N)，機電耦合常數( kp = 0.39)，殘留極化值( Pr = 21 μC/cm2)，O相轉T相溫度(TO-T = 110 °C), 以及居理溫度( TC = 333 °C)。

關鍵字

非鉛 ； 鈮酸鹽基 ； 鈣鈦礦結構 ； 壓電特性

並列摘要

With the riising attention of the environmental sense, some materials which contain harmful health elements should be inhibited. For the piezoelectric materials, new lead-free piezoelectric materials with better electrical properties to substitute for lead-containing materials. (K0.5Na0.5)NbO3 (KNN) is considered to be one of the most promising candidates for lead-free piezoelectric ceramics because of its very high Curie temperature (420℃) and large electromechanical coupling factors (kp ~ 0.36). For the purpose of further improving its properties, various amounts of CaTiO3 (CT) (0-7 mol%) were added into (Na0.5K0.5)NbO3 ceramics by using the conventional mixed oxide method in this study. The doped ceramics were characterized by X-ray diffraction analysis, scanning electron microscopy, X-ray photoelectron spectroscope, and Raman spectrometer to study their composition and microstructure. Their dielectric, piezoelectric and ferroelectric properties were also measured.
According to the changes of the crystal structure, phase transition, defect and electric properties with the composition variation, the relationship between physical and electric properties, even the possibility of application are also studied further in this thesis. Our experimental results showed that the addition of CaTiO3 is very effective in preventing the deliquescence and in improving the density and electric properties of the ceramics. The important results are summarized as the followings: First, (1-x) (Na0.5K0.5)NbO3 - x CaTiO3 solid solution system can be successfully synthesized and the relative density of sintered bulks of each composition can achieve 95% or over. At the doping amount of (x = 0.03 ), the ceramics with grain size of about 1 μm have the best domain switching ability. The leakage and X-ray photoelectron spectroscopy (XPS) results indicate that addition of CaTiO3 is very effective in preventing the deliquescence and to decrease the overall electrical conductivity, but it can increase oxygen ion conductivity. The best remnant polarization of (Pr = 21 μC/cm2) can be achieved for the ceramics with x = 0.03. The experimental results can demonstrate the relation of the MPB composition, electronnegativity and t value, consequently, providing a method for designing new piezoelectric materials. Second, the phase transformation is found to be changed with composition. The MPB, orthorhombic to tetragonal and TO-T near room temperature, appear at the ceramic of x = 0.03. This ceramic exhibits the optimum properties: d33 = 117 pC/N, kp = 0.39, Pr = 21 μC/cm2, and TC = 333 °C.

並列關鍵字

Lead-free ； (Na0.5K0.5NbO3)-base ； Perovskite ； Piezoelectric

參考文獻

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