本文選題：KNN基壓電陶瓷 + 線性組合規(guī)則��； 參考：《清華大學》2016年博士論文

【摘要】：本論文以Li,Ta和Sb共摻(K,Na)NbO_3(KNN-LTS)無鉛壓電陶瓷為研究對象,制備了高壓電性能的KNN-LTS無鉛壓電陶瓷,改善了陶瓷的燒結性能。研究了陶瓷中的電疇結構、原子結構與壓電性能之間的關系,探討了(K,Na)NbO_3基材料在多晶型相界(PPT)區(qū)間壓電性能增強的原因。首先利用“線性組合規(guī)則”預測(K,Na)NbO_3基材料的PPT相界。線性組合規(guī)則可以表述為n元系的PPT組分可以通過兩個(n-1)元系的PPT組分線性組合獲得。以此方法尋找到了KNN-LTS體系的PPT相界成分(Na0.52K0.4415Li0.0385)(Nb0.8735Ta0.064Sb0.0625)O_3,固相法制備的該成分陶瓷的壓電常數(shù)33d可達到359pC/N,高于文獻報導的平均水平。線性組合規(guī)則之所以能在(K,Na)NbO_3基陶瓷中推廣,是因為在兩個(n-1)元體系的PPT相界的連接線上,介電常數(shù)和極化強度會呈現(xiàn)相反的變化規(guī)律,導致壓電常數(shù)在中間某一點會出現(xiàn)峰值,從而獲得組元的PPT相界區(qū)間。實驗表明溶膠凝膠法制備的KNN-LTS納米粉體的燒結溫度低、燒結區(qū)間寬。(Na0.52K0.4425Li0.0375)(Nb0.86Ta0.06Sb0.08)O_3組分納米粉體燒結的陶瓷致密度高、成分均勻,33d約為424pC/N,2kV/mm下的逆壓電常數(shù)*33d約為680pm/V。同配方固相法制備的陶瓷的33d僅有342pC/N,2kV/mm下的*33d僅有490pm/V。研究發(fā)現(xiàn)在納米粉制備的陶瓷中存在大量尺寸為20~40nm的納米電疇,這種納米電疇的疇壁能比較低,在電場的作用下很容易運動,增強了陶瓷高場下的壓電活性。利用X射線吸收精細譜對不同晶體結構(K,Na)NbO_3基陶瓷的B位原子與近鄰氧原子的鍵長進行研究。發(fā)現(xiàn)在單相區(qū)間內(nèi),陶瓷有三個不同的B-O鍵鍵長;在PPT相界內(nèi),陶瓷有多于三個的不同B-O鍵鍵長。證實陶瓷在PPT相界內(nèi)自發(fā)極化方向增多,電疇易翻轉,壓電性能得以增強。通過分析中低場強和高場下KNN-LTS陶瓷的機電性能,分別研究了疇壁平移和電疇翻轉在不同相結構陶瓷中對壓電性能的貢獻,從而建立了陶瓷的宏觀機電性能與微觀電疇結構之間的關系。并發(fā)現(xiàn)極化后陶瓷在PPT相界區(qū)間內(nèi),疇壁的平移運動比較困難,電疇的翻轉運動比較容易。因而PPT相界高壓電活性主要來源于電疇的翻轉運動。
[Abstract]:In this paper, KNN-LTS lead-free piezoelectric ceramics with high piezoelectric properties were prepared, and the sintered properties of the ceramics were improved by taking the lead-free piezoelectric ceramics of Li Ta and SB co-doped KnbO3KNN-LTSas as the research object. The relationship between domain structure, atomic structure and piezoelectric properties in ceramics was studied. The reasons for the enhancement of piezoelectric properties in the polycrystalline phase boundary (PPTT) region were discussed. At first, the PPT phase boundary of the NbO _ 3 based material is predicted by using the "linear combination rule". The linear combination rule can be expressed as the PPT component of the n-element system, which can be obtained by the linear combination of two PPT components of the n-1) system. By this method, the phase boundary component of PPT in KNN-LTS system, Na0.52K0.4415Li0.0385Nb0.8735Ta0.064Sb0.0625O3, has been found. The piezoelectric constant of the ceramics prepared by solid phase method can reach 359pC / N in 33d, which is higher than the average level reported in literature. The reason why the linear combination rule can be popularized in PPT ceramics is that the dielectric constant and the polarization intensity of the PPT phase boundary of the two PPT element systems show the opposite law of variation, which leads to the peak of the piezoelectric constant at a certain point in the middle. Thus, the PPT phase boundary interval of the component is obtained. The results show that the sintering temperature of KNN-LTS nano-powders prepared by sol-gel method is low, the sintering range is wide. Na0.52K0.4425Li0.0375% Nb0.86Ta0.06Sb0.08O3 nano-powder sintered has high density, and the inverse piezoelectric constant of about 424pC / N2kV / mm is 680pmV. The ceramic prepared by the same formula solid state method has only 342pC / Nu 2kV / mm for 33d and only 490pm / v for 33d. It is found that there are a large number of nanocrystalline domains with the size of 20~40nm in the ceramics prepared by nano-powders. The domain wall energy of the nanocrystalline domains is relatively low, and it is easy to move under the action of electric field, which enhances the piezoelectric activity of the ceramics in high field. The bond length between the B atom and the nearest oxygen atom in different crystal structure of Knai NaN NbO 3 based ceramics was studied by means of X-ray absorption fine spectrum. It is found that there are three different B-O bond lengths in the single-phase region and more than three different B-O bond lengths in the PPT boundary. It is proved that the spontaneous polarization direction of the ceramics increases in the PPT phase boundary, the domain is easily flipped over, and the piezoelectric properties are enhanced. By analyzing the electromechanical properties of KNN-LTS ceramics with low and low field strength and high field, the contribution of domain wall translation and domain flipping to piezoelectric properties in different phase structure ceramics was studied. The relationship between macroscopic electromechanical properties and micro domain structure of ceramics was established. It is also found that the translation of domain walls is difficult in the PPT phase boundary region, and the domain flipping is easier. Therefore, the high piezoelectric activity of the phase boundary of PPT is mainly derived from the flipping motion of the domain.
【學位授予單位】：清華大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TQ174.1

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