【作者】 钟海胜；

【导师】 李强；

【作者基本信息】 武汉理工大学 ， 材料学， 2003， 硕士

【摘要】 铅基弛豫铁电材料具有优异的介电、压电和电致伸缩性能，是一类具有广泛应用前景的新型功能材料。本文采用二次合成法制备了复合钙钛矿结构的铌镁酸铅-钛酸铅（1-x）Pb(Mg_1／3Nb_2／3)O₃-xPbTiO₃（简称PMN-PT，其中0≤x≤1）粉料，并以此预合成的粉料制得PMN-PT弛豫复合钙钛矿相铁电陶瓷。利用常量化学分析法、XRD、SEM和DTA／TGA等分析测试技术，结合PMN-PT陶瓷密度和压电等性能的测试，对材料组分、结构与性能特征进行系统研究。 采用二次合成法制备PMN-PT钙钛矿相，避免了PbO和Nb₂O₅的直接反应，从而抑制了焦绿石相的生成。二次合成法能降低钙钛矿相的合成温度，减少PbO的挥发。PMN-PT钙钛矿相合成的合适工艺为：MgO过量2％（mol），1000℃保温4小时可合成单一相的先驱体MgNb₂O₆；以先驱体MgNb₂O₆、TiO₂、过量5％（mol）PbO为原料，850℃保温4小时，即可得到PMN-PT钙钛矿相。 采用预合成的陶瓷粉料，经球磨、成型、排塑、铅保护气氛烧结等工艺，制得PMN-PT弛豫复合钙钛矿相铁电陶瓷。测试结果表明：组分为0.65PMN-0.35PT陶瓷的密度达到8.10g／cm³，压电常数达到640pC／N。 采用定量化学分析法对PMN-PT中的阳离子进行滴定分析。pb²⁺的化学分析结果表明：在850℃下合成PMN-PT钙钛矿相时，氧化铅的挥发量极少。在1200℃高温下烧结PMN-PT陶瓷时，氧化铅的挥发量达到3.9％（wt），而在同样条件下采用同组分的粉料埋烧时，氧化铅的挥发将大为降低。 DTA／TGA分析结果表明：PMN-PT体系在650℃就开始形成钙钛矿相，在1200℃的条件下，PMN-PT钙钛矿相会有少量的铅挥发。热处理实验表明，合成的PMN-PT钙钛矿相在很宽的温度范围内是稳定的。 在PMN-PT系统中，随着PT含量的增加，2 θ=45°的XRD特征峰出现明显峰宽化现象，表明PMN-PT由三方相逐步向四方相转化。材料的性能研究表明，在PT含量x=0.30～0.35范围内，存在一准同型相界（Morphotropic Phase Boundary，简称MPB），此时材料表现出优异的压电性能。当三方相和四方相的比例接近1：1时，材料的压电常数达到最高。更多还原

【Abstract】 As a new-style functional material with promising applications in many fields, lead-based relaxor ferroelectrics could perform higher dielectric, piezoelectric and electrostrictive properties. In this paper, perovskite ferroelectrics of （l-x）Pb(Mg_1/3Nb_2/3)O3-xPbTiO3 （PMN-PT, O≤x≤l） have been prepared by the precursor method. And relaxor ferroelectric PMN-PT ceramics with compelx perovskite structure have been obtained successfully from the pre-synthesized powders. Combing with d₃₃ test and density measure, the composition, structure and properties of the PMN-PT ceramics have been studied systematically by means of macro-quantity chemical analysis, X-ray diffraction （XRD）, scanning electron microscope （SEM）, differential thermal analysis （DTA） and thermogravimetric analysis （TGA）.The precursor method could solve the problem that the appearance of pyrochlore phase during the synthesis procedure by avoiding the direct reaction between PbO and Nb₂O₅. Furthermore it also could decrease calcination temperature and PbO volatility. The homogenous precursor of MgNb₂O₆ was prepared at l000℃ for 4 hrs with excess 2%（ mol） MgO. And then complex perovskite PMN-PT could be synthesized at 850℃ for 4hrs with excess 5%（mol） PbO.The relaxor ferroelectric PMN-PT ceramics have been fabricated from pre-synthesized PMN-PT powders by ball milling, moulding, removing binder and sintering under the atomosphere of PbO. The results of study revealed that 0.65PMN-0.35PT ceramics exhibited maximum piezoelectric coefficient d₃₃640pC/N and density 8.10 g/cm3.The composition of obtained PMN-PT have been analyzed by means of macro-quantity chemical analysis. The analyzed results of the Pb2+ concentration indicated that PbO in the PMN-PT seldom volatilized at 850℃. The PbO volatility loss could be up to 3.9%（wt） when sintered at 1200℃. The loss of PbO was very minute when PMN-PT was sintered at 1200℃ while the samples buried in the powders with the same composition.DTA/TGA analysis indicated that the perovskite PMN-PT could be formed at 650℃. And the loss of PbO would be sharply increased from the temperature of 1200℃. The perovskite PMN-PT was heat-treated under various temperature from 650℃ to 1200℃. The results of XRD analysis demonstrated that the perovskite PMN-PT was rather stable in a large temperature scale.The XRD peak of 2 6 =45 ?was gradually widened with the increasing of PT. It might mean that rhombohedral phase was gradually converted to tetragonal phase in this system. Near x=0.30⁰.35 of the PT content, there was a morphotropic phase boundary （MPB） where the PMN-PT materials could be characterized with remarkable piezoelectric properties. Further study showed that the piezoelectric coefficient d₃₃ could be up to maximum value when the amountof the rhombohedral phase approached to that of the tetragonal phase in the PMN-PT system.更多还原