【作者】 李亚利；

【导师】 惠春； 李永祥；

【作者基本信息】 上海交通大学 ， 微电子学与固体电子学， 2012， 博士

【摘要】 随着环境保护越来越受到世界各国的重视，无铅压电陶瓷作为一种环境友好型材料，其研究已成为目前材料领域的热点之一。然而，通过掺杂改性方法对无铅压电陶瓷材料性能的提高有限，陶瓷的织构化控制是提高无铅压电陶瓷性能的有效的方法。很多实验证明，在某一极化方向拥有高度晶粒取向（高织构度）的压电陶瓷将表现出大幅优于非织构化陶瓷的电性能。本论文主要采用丝网印刷反应模板晶粒生长（screen-printing reactive templatedgrain growth，缩写为Sp-RTGG）技术，制备了具备<001>择优取向生长的钙钛矿结构铌酸钾钠（K,Na）NbO₃（KNN）和钨青铜结构铌酸铋钾K₂BiNb₅O₁₅（KBIN）织构化陶瓷。论文主要研究了丝网印刷反应模板晶粒生长技术的工艺过程和原理、模板晶粒的合成、影响陶瓷织构度的因素、织构化陶瓷的显微结构和电性能。论文中主要研究内容如下：（1）总结出一条有效的丝网印刷反应模板晶粒生长技术工艺流程，包括：丝网印刷网眼参数的选择，印刷浆料的配置，基体粉末的制备，模板晶粒的分散，切片和叠层，排胶工艺，以及陶瓷坯体的致密化方式等。提出了丝网印刷反应模板晶粒生长法制备织构化陶瓷的反应机理，其中印刷界面的存在不仅保证了模板晶粒的有效定向，更对其取向生长起着重要作用。（2）以铋层状结构Bi2.5Na3.5Nb5O18为前驱体，采用拓扑微晶置换法合成片状的钙钛矿结构NaNbO₃模板晶粒；采用熔盐法合成出片状的K₄Nb₆O₁₇晶粒，研究了其吸水特性；以K₄Nb₆O₁₇为前驱体通过拓扑微晶置换反应法合成钙钛矿结构片状的KNN晶粒，并研究了层状结构的K₄Nb₆O₁₇通过拓扑微晶置换反应生成KNN晶粒的反应机理；通过熔盐法制备了柱状的KBIN晶粒，研究了其中料/盐比和合成温度对晶粒尺寸的影响，给出了KBIN晶粒在熔盐中的生长机理。（3）以10mol%片状NaNbO₃为模板晶粒，0.5mol%K₄CuNb₈O₂₃为烧结助剂，采用丝网印刷反应模板晶粒生长技术成功地制备了<001>方向晶粒取向度为95%的织构化(K_0.45Na_0.55)NbO3陶瓷，研究了烧结温度和升温速率对陶瓷织构度的影响；SEM分析结果表明，织构化(K_0.45Na_0.55)NbO3陶瓷晶粒呈规则的砖块状，并沿着丝网印刷方向定向排列；相比于传统的固相反应法制备的非取向陶瓷，丝网印刷技术制备的(K_0.45Na_0.55)NbO3织构化陶瓷的压电性能取得明显提高：在sp（//）面上，介电常数εr，压电系数d33，机电耦合系数kp分别提高了75%，44%，42%，在sp（）面上，它们的提高幅度相对较小，分别为35%，30%，35%，在sp（//）面上的电性质明显优于sp（）面。（4）以10mol%片状NaNbO₃为反应模板晶粒，0.5mol%CuO为烧结助剂，采用丝网印刷反应模板晶粒生长技术制备了织构度为93%，d33和kp分别高达138pC/N和0.54的(K_0.5Na_0.5)NbO3陶瓷。研究了模板晶粒随烧结温度升高的生长过程，以及Ta原子的引入对陶瓷织构度的影响，发现Ta原子的引入对(K_0.5Na_0.5)NbO₃陶瓷的织构产生负面影响。（5）采用棒状模板通过丝网印刷反应模板晶粒生长技术制备出各向异性的织构化陶瓷。采用15mol%棒状KBIN为模板晶粒，通过丝网印刷反应模板晶粒生长技术首次制备出沿<001>方向织构度为45%的KBIN陶瓷，介电性能分析结果显示其具备明显各向异性。更多还原

【Abstract】 With increasing attention to environmental protection globally, as a type ofeco-friendly materials，lead-free piezoelectric ceramics have become one of the hot areasof current materials research. However, the doping method has been unable to keep upwith the pace of performance improvement of ceramic, the texture control ofpolycrystalline ceramics is a convenient and effective approach to improve thepiezoelectric properties of lead-free ceramics. Many reports show that piezoelectricceramics with a high degree of grain orientation in a certain polar direction will exhibitsignificantly better performances compared to those of non-textured ceramics.In this disertation，screen-printing reactive templated grain growth （Sp-RTGG） wasstudied to fabricate the textured perovskite-structured （K,Na）NbO₃（KNN） andtungsten-bronze-structured K₂BiNb₅O₁₅（KBIN） ceramics with a preferred grainorientation in the <001> direction. The screen-printing process, the mechanism ofscreen-printing reactive templated grain growth, the synthesis of template, the factorsaffecting the texture degree, the microstructure, and the electrical properties of thetextured ceramics are studied in detail. The main contents are as follows:（1） We study the complete process of screen-printing reactive templated graingrowth and introduces an effective process flow, including: the parameter selection ofscreen-printing mesh, the configuration of screen-printing ink, the preparation of matrixpowder, the dispersion of template, sliced and stacked, the process of binder removal, andthe densification method of ceramic green body. Proposing the reaction mechanism ofscreen-printing reactive templated grain growth, in which the existence of printing interfaces not only make template grains effectively oriented but also plays an importantrole in their oriented growth.（2） Plate-like perovskite-structured NaNbO₃templates were synthesized by thetopo-chemical microcrystal conversion （TMC） method, using bismuth layer-structuredBi2.5Na3.5Nb5O18as precursors. Plate-like K₄Nb₆O₁₇particles were obtained by the moltensalt synthesis, and the behavior of adsorption layer of water on K₄Nb₆O₁₇was studied.Plate-like perovskite-structured KNN particles were synthesized by the topo-chemicalmicrocrystal conversion method, using layer-structured K₄Nb₆O₁₇as precursors.Furthermore, the topo-chemical reaction mechanism from K₄Nb₆O₁₇to KNN was alsoinvestigated. Rod-like KBIN particles were synthesized by the molten salt synthesis, theinfluence of powder/salt and reaction temperature on the particle size of KBIN werestudied, and the growth mechanism of KBIN in molten salt was proposed.（3） Textured (K_0.45Na_0.55)NbO₃lead-free piezoelectric ceramics exhited both a highgrain orientation （Lotgering factor F=95%） along <001> direction and a relative highdensity （92%of theoretical density） have been successfully fabricated by thescreen-printing reactive templated grain growth technique, using10mol%plate-likeNaNbO₃templates and0.5mol%K4CuNb8O23sintering aids. The influence of sinteringtemperature and heating rate on grain orientation degree were investigated. SEM imagesshow that the textured ceramics is composed of well-ordered brick-like grains arrangedalong the screen-printing direction. The piezoelectric properties of the textured(K_0.45Na_0.55)NbO₃ceramics were significantly improved compared to non-texturedsamples: the dielectric constant εr, piezoelectric constant d33, and electromechanicalcoupling coefficient kpwere increased by about75%,44%and42%in （sp//） plane, andthose were increased by about35%,30%and35%in<001> orientation （F=93%）were fabricated by the screen-printing reactive temp （sp） plane, respectively.（4） Highly textured (K_0.5Na_0.5)NbO₃ceramics with lated grain growth technique, using10mol%plate-like NaNbO₃templates and0.5mol%CuO sintering aids. The textured (K_0.5Na_0.5)NbO3ceramics showed very high piezoelectric constant d33=133pC/N, andhigh electromechanical coupling factor kp=0.54. The growth process of template grainwith sintering temperature increasing and the influence of Ta atom on grain orientationdegree were studied. It was found that the introduction of Ta atoms had a negative impacton the grain orientation degree of (K_0.5Na_0.5)NbO3textured ceramics.（5） The work focuses on the fabrication of anisotropic textured ceramics with rod-liketemplates using screen-printing reactive templated grain growth technique. TexturedKBIN ceramics were first successfully fabricated by this method, using15mol%rod-likeKBIN templates. The textured KBIN ceramics showed an orientation degree of45%along<001> direction. The analysis of the dielectric properties of the textured KBIN ceramicsrevealed obvious anisotropies.更多还原