KNN基无铅压电陶瓷在多晶型相界附近的结构与性能

发布时间：2018-05-04 00:37

本文选题：KNN基压电陶瓷 + 线性组合规则　；参考：《清华大学》2016年博士论文

【摘要】：本论文以Li,Ta和Sb共掺(K,Na)NbO_3(KNN-LTS)无铅压电陶瓷为研究对象,制备了高压电性能的KNN-LTS无铅压电陶瓷,改善了陶瓷的烧结性能。研究了陶瓷中的电畴结构、原子结构与压电性能之间的关系,探讨了(K,Na)NbO_3基材料在多晶型相界(PPT)区间压电性能增强的原因。首先利用“线性组合规则”预测(K,Na)NbO_3基材料的PPT相界。线性组合规则可以表述为n元系的PPT组分可以通过两个(n-1)元系的PPT组分线性组合获得。以此方法寻找到了KNN-LTS体系的PPT相界成分(Na0.52K0.4415Li0.0385)(Nb0.8735Ta0.064Sb0.0625)O_3,固相法制备的该成分陶瓷的压电常数33d可达到359pC/N,高于文献报导的平均水平。线性组合规则之所以能在(K,Na)NbO_3基陶瓷中推广,是因为在两个(n-1)元体系的PPT相界的连接线上,介电常数和极化强度会呈现相反的变化规律,导致压电常数在中间某一点会出现峰值,从而获得组元的PPT相界区间。实验表明溶胶凝胶法制备的KNN-LTS纳米粉体的烧结温度低、烧结区间宽。(Na0.52K0.4425Li0.0375)(Nb0.86Ta0.06Sb0.08)O_3组分纳米粉体烧结的陶瓷致密度高、成分均匀,33d约为424pC/N,2kV/mm下的逆压电常数*33d约为680pm/V。同配方固相法制备的陶瓷的33d仅有342pC/N,2kV/mm下的*33d仅有490pm/V。研究发现在纳米粉制备的陶瓷中存在大量尺寸为20~40nm的纳米电畴,这种纳米电畴的畴壁能比较低,在电场的作用下很容易运动,增强了陶瓷高场下的压电活性。利用X射线吸收精细谱对不同晶体结构(K,Na)NbO_3基陶瓷的B位原子与近邻氧原子的键长进行研究。发现在单相区间内,陶瓷有三个不同的B-O键键长;在PPT相界内,陶瓷有多于三个的不同B-O键键长。证实陶瓷在PPT相界内自发极化方向增多,电畴易翻转,压电性能得以增强。通过分析中低场强和高场下KNN-LTS陶瓷的机电性能,分别研究了畴壁平移和电畴翻转在不同相结构陶瓷中对压电性能的贡献,从而建立了陶瓷的宏观机电性能与微观电畴结构之间的关系。并发现极化后陶瓷在PPT相界区间内,畴壁的平移运动比较困难,电畴的翻转运动比较容易。因而PPT相界高压电活性主要来源于电畴的翻转运动。
[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.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ174.1

【相似文献】