【作者】 刘瑾瑾；

【导师】 李江宇；

【作者基本信息】 湘潭大学 ， 材料物理与化学， 2007， 硕士

【摘要】 电材料作为重要的功能材料在电子材料领域占据相当大的比重。近几年来,铁电陶瓷在全球每年销售量按15%左右的速度增长。随着信息产业的飞速发展,铁电器件(变压器、存储器、换能器、驱动器、滤波器、谐振器、鉴频器等)已在音视频、通讯、电脑周边等领域大量应用。然而,环境问题现在已经广泛存在于全世界,世界范围的无铅化呼声日益高涨;同时,随着电子整机向数字化、高频化、多功能化和薄、轻、小、便携式的方向发展,以铅为主的铁电器件正面临着前所未有的挑战。本文正是以此为切入点,从介观到宏观尺度,对铁电材料及铁电器件进行了深刻的研究。我们制备了铁电薄膜材料,系统总结和优化工艺参数;分析了一种应用于变压器的新型结构的压电陶瓷板;并从理论上对铁电材料的宏观性能与其介观尺度内部组织之间的关系做了一些有意义的探讨。本论文的主要工作如下:1.采用化学溶液沉积法(CSD)制备出纯铋层状钙钛矿结构的BNT(Bi3.50Nd0.50Ti3O12)无铅铁电薄膜,用X射线衍射仪分析了BNT薄膜的晶体结构;用扫描电镜(SEM)对BNT薄膜表面形貌进行了表征,并得到了薄膜的厚度等信息;用RT66A铁电测试仪测量分析BNT薄膜的铁电性能;用HP4194A测量分析BNT薄膜的介电性能。电滞回线表明我们制备的BNT薄膜具有大的剩余极化强度,适合做非挥发性铁电存储器。2.分析了一种应用于压电变压器的电强迫厚度扭转振动矩形陶瓷板,利用线形压电理论,得到了其三维方程的一个解析解,并计算了该压电变压器的变压比,输入电导以及工作效率与系统参数之间的关系。3.提出了一种铁电晶体增强压电性能的理论机制:综合利用铁电体本征的晶体各向异性以及外在的铁电变体的90°畴翻转。基于能量最小化的原理,分析计算了在不同的晶体学取向下,钛酸钡单晶的工程畴结构及其本征的和外在的压电反应,计算结果表明:外在的铁电变体的90°畴翻转极大地增大了压电系数,尤其是在外加电场比较小,畴壁的运动可逆的情况下。同时,确定了最优化的极化方向。更多还原

【Abstract】 As one of the most important active materials, ferroelectric materials hold a large ratio in the field of electronic materials. The sales volume of ferroelectric ceramics in the world increases at about 15 percent in recent years. With the rapid development of information industry, ferroelectric devices, such as ferroelectric memory, transducer, actuator, filter, resonator, frequency discriminator, have been extensively applied in the field of audio, video, communication, and computer devices.However, environmental issues are world-widely concerned. Ferroelectric devices which is mainly made from lead materials are facing great challenges both for the voice from ever-rising environmental protection and the development trend of electronic devices along the digital, high-frequent, multifunctional, thin, light, small and portable direction. This dissertation takes this as the cutting point and makes a deep study in ferroelectric materials and devices from mesoscale to macroscale. We prepare ferroelectric thin films by chemical solution deposition method. We analyze a rectangular ceramic plate in electrically forced thickness-twist vibration as a piezoelectric transformer. Meanwhile, we explore the relationship between the macro behavior of ferrolectric materials and their inner microstructure in mesoscale.The main work of this dissertation is as follows:1. We prepared the lead-free BNT thin films by chemical solution deposition. Phase identification, crystalline orientation and degree of crystallinity of the films were studied by a D/max-rA X-ray diffractometer. Scanning electron microscopy(SEM) was used to determine the thickness and the surface morphology of the thin films. The ferroelectric and dielectric measurements were performed using a RT66A ferroelectric tester and a HP4194A impedance analyzer equipped with a micrometer probe station. P-E hysteresis loop showed the chemical solution deposition derived BNT thin films were a potentially important candidate for non-volatile random access memory devices.2. A rectangular ceramic plate with appropriate electrical load and operating mode is analyzed for piezoelectric transformer application. An exact solution from the three-dimensional equations of linear piezoelectricity is obtained. The solution simulates the real operating situation of a transformer as a vibrating piezoelectric body connected to a circuit. Transforming ratio, input admittance, and efficiency of the transformer are obtained.3. We propose a mechanism for enhanced piezoelectricity that takes advantage of both intrinsic crystalline anisotropy of ferroelectric crystal and extrinsic 90°domain switching of ferroelectric variants. The intrinsic and extrinsic piezoelectric responses of barium titanate single crystals under different crystallographic orientations are calculated using an energy minimization theory, where it is observed that the piezoelectric coefficient is significantly enhanced by the 90°domain switching, especially under the small field measurement where the domain wall movement is reversible. The optimal crystallographic orientation is also identified.更多还原