【作者】 李均；

【导师】 周忠祥； Ruyan Guo；

【作者基本信息】 哈尔滨工业大学 ， 光学， 2013， 博士

【摘要】 随着科学技术的日益发展，作为人类社会发展基础产业的材料科学必须紧跟时代步伐。近年来压电材料备受关注，特别是目前大规模应用的锆钛酸铅陶瓷，然而为了人类的环境和可持续发展，寻找一种无铅压电铁电材料来替代锆钛酸铅成为了当代相关领域科研人员的当务之急和时代使命。近十年里在国际铁电领域中，无铅压电陶瓷被大量地开发和改性，但距离在应用中取代锆钛酸铅陶瓷还相差甚远，怎样进一步提高无铅材料的性能和稳定性就是大家努力的方向。众所周知，由于铁电单晶的高取向性，使其各项性能都远远超出同组分的陶瓷材料，而且铁电单晶的结构比陶瓷简单，便于进行基于晶体取向变化物理机理的研究。而钽铌酸钾晶体作为最早被发现的光折变材料，是一种为大家熟知的固熔体。截止目前，关于钽铌酸钾晶体绝大多数的研究工作都集中在光学性能上，而其系统性的电学性能（介电、热释电、压电和铁电性质）却鲜有报道。而且直到现在，关于钽铌酸钾晶体的研究都集中在富钽区域，而关于富铌区域的研究却很少。因此，本论文将有机地结合无铅压电铁电材料的开发背景和钽铌酸钾晶体的研究现状，通过分析钽铌酸钾晶体的合成和组分相图，采用顶部籽晶熔体法生长了一系列大尺寸、高质量、富铌掺锂的钽铌酸钾晶体，即钽铌酸钾锂晶体(（K,Li）(Ta_1-xNb_x)O₃，KLTN)，继而开展其各项研究工作。对无铅晶体KLTN的组分和结构进行分析和研究。利用能量色散谱分析（EDS）测试晶体的组分；利用X射线衍射技术（XRD）表征晶体结构，并分析了晶格常数的演变规律和掺铁KLTN（Fe: KLTN）晶体的占位情况；对无铅晶体KLTN的介电行为进行系统地表征和研究。通过对所有组分晶体沿不同晶向在不同频率和大温区下的介电性能测试，明确KLTN晶体的相变机制、给出其所有相变温度的变化规律，并分析极化过程对介电性能的影响；分析KLTN晶体的弥散相变特性，并给出具体的弥散指数；对KLTN晶体的介电可调谐性能进行研究，分析介电常数和损耗随外加偏置电场的变化行为。通过研究无铅晶体KLTN的热释电和铁电性能对其自发极化特性进行分析。通过对无铅晶体KLTN热释电性能的表征，进一步确认其相变规律的同时给出自发极化在全温区的变化行为。利用压电响应力显微镜（PFM）对富铌KLTN晶体的表面形貌和铁电畴进行观察；利用铁电测试仪对富铌KLTN晶体的电滞回线进行表征，得到其矫顽场和剩余极化强度，分析其变化规律和原因。结合热释电和电滞回线的测试结果对KLTN晶体的自发极化特性进行机理分析。对无铅晶体KLTN各种振动模式下的压电性能进行系统地研究。制作富铌KLTN晶体横向长度振动模式、厚度振动模式、纵向振动模式以及横向切变模式的压电振子，给出和分析相关的压电、机电耦合和弹性性能参数，并与传统的压电材料进行对比；利用超高频振动计，分析其谐振行为，得到谐振频率下三维微观形貌。对无铅晶体KLTN各项性能的晶向依赖特性进行计算和模拟，绘制其三维分布图。更多还原

【Abstract】 With the growing development of science and technology, as a basic industryfor the development of human society, material science should keep abreast of thetimes. As large-scale application currently is lead-zirconium-titanate, piezoelectricmaterial is a major concern in recent years; for the environment and sustainabledevelopment, looking for lead-free piezoelectric ferroelectric materials to replace itis contemporary and historical mission of the researchers in the related field. In thepast ten years, there are mass exploitations of lead-free piezoelectric ceramics andtheir modification in the area of international ferroelectric, but replacing thelead-zirconate-titanate ceramics to application is too early; thus, the emphasis focuson how to further improve the performance and stability of lead-free materials.Due to its high orientation, the performance of ferroelectric single crystals isfar beyond that of the same composition of ceramics; moreover, the structure offerroelectric single crystal is simpler than that of ceramic, as well as convenient toresearch on orientation-dependent physical mechanism. Potassium tantalum niobatecrystal is a well-known solid solution in photorefractive material, the vast majorityof research is focused on the optical properties; however, systemic electricalproperties (dielectric, pyroelectric, piezoelectric and ferroelectric properties) arerarely reported. And until now, research has focused on the tantalum-rich potassiumtantalum niobate crystal; niobium-rich regions have not been studied.Thus, combining the development background of lead-free piezoelectric andferroelectric material and research status of potassium tantalate niobate crystal, andthrough analysis synthesis and compositional phase diagram of potassium tantalumniobate crystal, a series of big sized, high quality, and niobium-rich lithium-dopedof potassium tantalum niobate crystals (potassium lithium tantalum niobate singlecrystals,(K,Li)(Ta1-xNbx)O3, KLTN) have been obtained using top-seeded meltgrowth method), and then carried out their research work. The composition,structure, and thermal expansion performance of niobium-riched KLTN crystals areanalyzed. The compositions are determined using energy dispersive spectrometry(EDS); crystal structures are characterized using x-ray diffraction (XRD), and theevolution of lattice parameters and the replacement of Fe: KLTN crystals are alsoanalyzed.Dielectric property of lead-free crystals KLTN is comprehensivelycharacterized. Through dielectric performance of all compositions along differentcrystal orientation in different frequency and large temperature range, phase transition mechanism of niobium-rich KLTN crystals are determined, and all ofphase transition temperatures are obtained; poling process for dielectric property isdiscussed; diffusion characteristics of niobium-rich KLTN crystals are analyzed;dielectric tunability of KLTN crystals is characterized, and the behavior of dielectricconstant and loss under dc bias is determined.The Polarization properties of lead-free crystals KLTN are analyzed throughtheir pyroelectric and ferroelectric properties. Pyroelectric properties ofniobium-rich KLTN single crystal are determined; the phase transition points arefurther confirmed; the spontaneous polarizations in the whole temperature range arecomputed, and are compared with the total polarization obtained in themeasurement of thermal expansion. The ferroelectric P-E hysteresis loops ofniobium-rich KLTN crystals are measured, and their coercive field and the remnantspontaneous polarization are determined. Combined pyroelectric property andhysteresis loops, spontaneous polarizations have been theorically analyzed.Piezoelectric properties of niobium-rich KLTN single crystals are determined.The piezoelectric vibrators of horizontal length vibration mode, thickness vibrationmode, vertical vibration mode and horizontal shear mode of niobium-rich KLTNsingle crystals are made; piezoelectric constant and electro-mechanical couplingfactor are determined, and also compared with those of traditional piezoelectricmaterials. The vibration behavior of KLTN crystals is analyzed using ultrahighfrequency vibration meter, and the surface profile at resonant frequency is obtained.The surface morphology and ferroelectric domains of niobium-rich KLTN crystalsare observed using piezoelectric response force microscopy (PFM).更多还原