铌酸钾钠基无铅铁电单晶的生长及性能研究

发布时间：2018-06-28 23:20

  本文选题：铌酸钾钠 + 晶体生长　； 参考：《上海应用技术大学》2017年硕士论文

【摘要】：压电材料广泛应用于日常生活中,其中PZT基压电陶瓷的市场占有率超过90%。随着环境保护意识日益深入人心,现有压电材料中大量的铅对环境产生巨大危害,应用将逐步受到限制,发展无铅压电材料近年来成为研究的热点。在众多无铅压电材料中,KNN基压电材料以其相对较高的压电系数、机电耦合系数,特别是较高的居里温度,使其在应用中具有一定优势,被认为是最有希望替代PZT的无铅压电材料体系。本论文以KNN基单晶为研究对象,从晶体的生长、加工到其结构和性能的关系等方面进行系统的研究。采用顶部籽晶助溶剂提拉法(TSSG)生长KNN基单晶。在生长初期没有籽晶的情况下,选择铂丝作为籽晶,初步生长了 KNN晶体。并且通过控制合适的工艺参数,成功生长大尺寸,高质量的(KxNa1-x)Nb03 (简称为KNN)单晶以及掺杂MnO_2的(KxNa1-x)NbO3x%MnO_2 (简称为KNN-x%MrnO_2)单晶。通过定向、切片等后续加工得到了尺寸较大的(001)晶片。通过粉末XRD对晶体的结构进行分析,测试结果表明所生长的KNN和KNN-x%MnO_2单晶均为纯的钙钛矿结构,室温下为正交相,无杂相生成。对单晶的(001)的介电、压电、铁电等电学性能进行研究。通过单晶的升温介电温谱研究,结果表明晶体在升温过程中主要存在两个介电异常峰,分别对应正交铁电相到四方铁电相转变和四方铁电相到立方顺电相相变。纯的KNN单晶的室温下的介电常数约为168,介电损耗tanδ为0.2,晶体更趋向于正常铁电体;而掺杂MnO_2后,室温下的介电常数增大,介电损耗降低,晶体更趋向于弛豫铁电体。并且掺杂一定量的MnO_2后,晶体的压电系数KNN-0.5%MnO_2单晶d33由161pC/N升高到191pC/N;若在600℃下对晶体进行退火处理,其压电常数有所增大,d33为261pC/N。灿杂MnO_2后,晶体的矫顽场降低,剩余极化强度有所增大。采用升温拉曼散射研究了 KNN单晶的晶格振动变化,研究了温度变化对晶格振动模的影响。通过升温过程中峰的个数,以及峰形的变化确定相变,从常温下的正交相(Amm2)到四方相(P4bm)再到顺电相即立方相,这和介电温谱的结果一致。通过改变实验光路配置,将四方相单晶不同的振动模式峰分离,确定每个峰所对应的振动模。
[Abstract]:Piezoelectric materials are widely used in daily life, among which PZT-based piezoelectric ceramics have more than 90% market share. With the increasing awareness of environmental protection, a large amount of lead in the existing piezoelectric materials will cause great harm to the environment, and its application will be restricted gradually. The development of lead-free piezoelectric materials has become a hot topic in recent years. In many lead-free piezoelectric materials, KNN based piezoelectric materials have some advantages in application because of their relatively high piezoelectric coefficient, electromechanical coupling coefficient, especially the higher Curie temperature. It is considered to be the most promising alternative to PZT. In this paper, KNN-based single crystals are studied systematically, from the growth and processing of crystals to the relationship between structure and properties. KNN based single crystals were grown by the top seed cosolvent Czochralski method (TSSG). In the case of no seed crystal at the beginning of growth, the KNN crystal was grown with platinum wire as seed crystal. By controlling the appropriate technological parameters, large size (KxNa1-x) Nb03 (KNN) single crystals and (KxNa1-x) Nb3xMnO2 (KNN-xMrnO2) single crystals have been successfully grown by controlling appropriate technological parameters, as well as (KxNa1-x) NbO3xMnO2 (KNN-xMrnO2) single crystals doped with MnO _ (1-x) NbO _ 3xMnO _ 2. The larger (001) wafer was obtained by the following processing such as orientation, slicing and so on. The crystal structure was analyzed by powder XRD. The results showed that the KNN and KNN-xx MNO _ 2 single crystals were pure perovskite structure at room temperature. The dielectric, piezoelectric and ferroelectric properties of single crystal (001) were studied. The results show that there are mainly two abnormal dielectric peaks in the process of heating, which correspond to the transition from quadrature ferroelectric phase to tetragonal ferroelectric phase and tetragonal ferroelectric phase to cubic paraelectric phase transition. The dielectric constant of pure KNN crystal is about 168 at room temperature, the dielectric loss tan 未 is 0.2, and the crystal tends to be normal ferroelectrics, but after doping MNO 2, the dielectric constant increases at room temperature, the dielectric loss decreases, and the crystal tends to relaxor ferroelectrics. After doping a certain amount of MnO-2, the piezoelectric coefficient of the crystal KNN-0.5and MnO-2 single crystal d33 is increased from 161pC / N to 191pC / N, and if annealed at 600 鈩，

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