微觀結構和電學性質於非鉛陶瓷鹼金族鈮酸鹽基之研究

Study on Microstructures and Electrical Properties of Na0.52K0.48NbO3-base Lead-free Ceramics

劉陽耀(Yang-Yao Liu)

指導教授 ： 曾俊元 ； 周振嘉

國立臺北科技大學/工程學院/材料科學與工程研究所/碩士(2008年)

https://doi.org/10.6841/NTUT.2008.00455

摘要

近來隨著環保意識高漲，使得含有對人體之健康有疑慮元素的材料將會被逐步禁用，例如鉛、鎘、汞、六價鉻等材料。於電子陶瓷中影響最大的將會是壓電陶瓷，由於現今壓電陶瓷所使用的材料最大宗為 PZT，而這類含鉛之材料雖然早在數年前就被明令將被禁用，但由於其替代品開發之困難，故至今其限期不斷在延後，但尋找可替代之材料仍為現今刻不容緩之議題。
在無鉛壓電陶瓷近幾年中，主要以鈦酸鉍納鉀 (Na0.5Bi0.5)TiO3 及鈮酸鈉鉀 (Na1-xKxNbO3 [NKN]) 為主的固溶系統系列，但是鈮酸鈉鉀等材料由一般陶瓷製程較無法得到緻密性結構，由於相穩定度受限於 1140 ℃，所以不能在較高溫度燒結，導致於陶瓷體密度較低相對的電特性就較差。最近文獻發現鈮酸鈉鉀，若添加屬於鐵電性鈣鈦礦 ABO3 結構的化合物，在一般空氣中燒結就可得到緻密性陶瓷。
修飾型鈮酸鈉鉀 [(K, Na)NbO3 based] 是一種高居禮溫度 (Tc) 、對溫度變化穩定、機電耦合因數高 (kp、kt) 的陶瓷材料，所以修飾型鈮酸鈉鉀陶瓷適合於感測器方面的應用。製作陶瓷的方法很多，有傳統氧化物混合法、溶膠-凝膠法(sol-gel)及熱均壓法等。目前最常被使用的是傳統氧化物混合法，因為其具有製程簡單、價格較低等特色。在另一方面，在近年來的相關文獻研究中亦可發現鈮酸鈉鉀固溶系統的陶瓷也具有弛緩性介電體的行為。此實驗主要是研究修飾型鈮酸鈉鉀陶瓷材料特性。
由本實驗的結果可以確定以下：第一、利用傳統固態氧化物方法，合成出修飾型鈮酸鈉鉀基陶瓷，化學成分為 (1-x)Na0.52K0.48NbO3-xCaTiO3 ， [x = 0~0.1] ，經由X光繞射儀檢測均屬於單一鈣鈦礦結構相存在的固溶系統。第二、此修飾行鈮酸鈉鉀隨成分變動，使晶體結構發生變化的過程，在添加量為 0.03~0.07 之間，逐漸由斜方晶相轉為正方晶相，且經由計算得到晶格參數以及理論密度。第三、得知隨著參雜量增多，越接近兩相共存區 (MPB) 時，其壓電特性有明顯的改變。

關鍵字

非鉛 ； 鈮酸鹽基 ； 鈣鈦礦結構 ； 壓電特性

並列摘要

Some materials containing with harmful health elements such as lead(Pb), cadmium(Cd), mercury(Hg), hexavalent chromium(Cr VI), are recently inhibited for industrial applications because of the consideration of environmental protection. At present, the most important piezoelectric ceramics is PZT, which contains Pb content. It needs to find other Pb-free piezoelectric, but owning to the difficulty of finding ceramics to substitute PZT. One of possible candidates is NKN ceramics.
However, (Na0.52K0.48)NbO3 ceramics sintered by ordinary sintering show relatively lower electrical properties due to the difficulty in obtaining dense ceramics by ordinary sintering in air. The phase stability is for potassium sodium niobate limited to 1140℃. High temperatures of sintering of NKN is therefore impossible to achieve dense ceramics. Furthermore, the volatility of potassium oxide makes its stoichiometry difficult to control the formation of extra phases leading to a quick disintegration of the final samples once exposed to humidity.
Modified potassium sodium niobate ceramic have good properties such as high Curie point (Tc), high temperature stability and high electromechanical constant (kp、kt), which is suitable to be used as surface acoustic wave (SAW) gas sensors. In this work, CaTiO3 is doped into (Na0.52K0.48)NbO3 to form the modified potassium sodium niobate ceramic system by the conventional oxide-mixed method. The effect of processing parameters on the properties of the ceramics is studied to find the optimal processing conditions.
(1-x) (Na0.52K0.48)NbO3-x CaTiO3 [x=0~1] ceramics can successfully be synthesized in this study. X-ray patterns of these ceramics show that all the samples belong to pure perovskite phase and no extra-peaks can be identified. We also study the phase transformation with composition variation of this system. The structure of the phase is changed from Octahedral phase to Tetragonal phase, when x between 0.03 and 0.07. Besides, the lattice parameters and theoretical densities of the ceramics are also obtained based on the data obtaining from XRD study. It is shown that the piezoelectric properties of these ceramics near the morphotropic phase boundary (MPB) region are superior than those of the ceramics on the other regions.

並列關鍵字

Lead-free ； Na0.52K0.48NbO3-base ； Perovskite ； Piezoelectric

參考文獻

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