【作者】 吕应刚；

【导师】 王春雷；

【作者基本信息】 山东大学 ， 凝聚态物理， 2008， 硕士

【摘要】 压电陶瓷是一类重要的功能材料,被广泛应用于制作压电超声换能器、陶瓷滤波器、蜂鸣器、各种传感器和压电高压发生器等换能器件,以及近年来被应用于纺织机械行业的双晶片结构压电选针机。由于目前实际应用的压电陶瓷主要是以锆钛酸铅（PbTiO₃-PbZrO₃）为主要成份的三元系材料,其中氧化铅的含量高达70%以上。铅基压电陶瓷工业在生产和使用后的处理过程中给人类的生存环境带来了不可忽视的污染,直接威胁到人类的健康。随着人们对环境保护问题的关注,解决压电陶瓷工业领域中的铅污染问题变得日益重要,所以实现压电陶瓷元器件的无铅或少铅化生产成为当务之急。本论文针对当前具有实用、环保意义的铌钽酸钾钠无铅压电陶瓷及其应用-无铅压电变压器这一典型器件,结合目前国际上该领域的研究现状,开展了较为系统深入的研究工作。本论文首先从材料设计入手,通过研究铌酸盐无铅压电陶瓷的各种物理性质和掺杂特性,寻找出综合性能优异的无铅压电陶瓷材料,并对其物理性能作出了合理的解释。其次,采用面向应用的研究思路,利用改性的压电陶瓷制备了圆盘型压电变压器。硕士期间的工作主要包含了铌钽酸盐压电陶瓷的改性研究,以及无铅材料在压电陶瓷变压器中的应用两大部分。铌钽酸盐压电陶瓷和无铅压电变压器是经过查阅大量相关科技文献而确定的研究对象,是本工作认为最有研究价值的一类无铅压电材料和具体压电器件。材料的制备方面,采用传统固相反应法制备了铌钽酸钾钠(（K,Na）（Nb,Ta）O₃（简写为KNNT）系列压电陶瓷,并研究了材料的制备条件、微观结构、介电性质和压电性质。其中,基础研究部分研究了Ta含量和K,Na比例变化对陶瓷微观结构、相变、以及介电、压电性质的影响;实用研究部分针对压电变压器对压电材料性能的要求,对KNNT做了掺杂改性研究。研究发现掺入适量K₄CuNb₈O₂₃（KCN）和MnO₂可以大幅度提高KNNT陶瓷的机械品质因数Q_m,有效降低介电损耗tgδ,使材料呈现明显的“硬”性压电陶瓷特性,从而可能替代铅基压电陶瓷在压电变压器中获得应用。最后得到了优化配方为:KNNT+1.0mol%KCN+0.5mol%MnO₂的高性能压电陶瓷,其机械品质因数Q_m=1563,介电损耗在测试频率1kHz下为tgδ=0.4%,机电耦合系数k_p=42.2%,压电常数d₃₃=96pC/N。采用机电等效网络方法分析了Rosen型压电变压器模型的等效电路,参考其空载升压比公式,选择适合制备变压器的改性KNNT陶瓷,制备了系列不同输入、输出电极面积比的圆盘型压电陶瓷变压器。研究了圆盘型压电变压器的阻抗特性和升压比特性,并对驱动电路做了初步研究。制备了圆盘型压电陶瓷变压器样机,并得到了超过42倍的最大空载升压比。更多还原

【Abstract】 Piezoelectric ceramics as one of the most important functional ceramic material is used in many practical applications, such as: piezoelectric ultrasonic transducer, piezoelectric ceramic filter, piezoelectric buzzer, different kinds of sensors, actuators, piezoelectric high voltage generators, etc. Recently piezoelectric needle selectors have been used for Jacquard knitting machine. Most piezoelectric ceramic materials in practical use are lead zirconate-titanate based systems. These materials contain more than 70% PbO by weight, so they cause environmental pollution during manufacture and after usage. It is well known, the environmental protection has been becoming an important issue for the governments and the public. Therefore, it is very essential to develop lead-free or lead-less content piezoelectric materials to solve the lead pollution in piezoelectric industry.After intensive and extensive survey, potassium sodium niobate-tantalate （KNNT） ceramics has been selected as materials for piezoelectric transformer. In this work, practicality, KNNT ceramics and piezoelectric transformer based on KNNT have been studied. From the start of designing piezoelectric materials, physical properties of KNNT ceramics was studied which aimed to find high performance KNNT materials for piezoelectric transformer. Reasonable explanation to the phenomena was given. Secondly, application-oriented research approach was chosen and disk-type piezoelectric transformer was fabricated using the modified KNNT ceramics.Ta-modified KNNT ceramics has been prepared using conventional solid-state reaction technique. Preparation conditions, microstructures, dielectric properties and piezoelectric properties were analyzed. The effects of the Ta content and K, Na ratio on the microstructures, phase transition and piezoelectric properties were studied. The doping of KCN and proper amount of MnO₂ was effective in promoting the mechanical quality factor Q_m and reducing the dielectric loss tanδ. It made KNNT ceramics possess "harder" properties. This material is a promising candidate for the lead-free piezoelectric transformer applications. The high performance KNNT piezoelectric materials was obtained, high mechanical quality of Q_m=1563, dielectric loss about tanδ=0.4% at 1kHz, electromechanical coupling coefficient of k_p=42.2% and piezoelectric constant d₃₃=96pC/N.The equivalent circuit model of Rosen-type piezoelectric transformer was analyzed using electrical and mechanical equivalent network method. With reference to its voltage gain formula, optimal KNNT ceramics was chosen for transformer. Disk-type piezoelectric transformers with different input and output area ratio were fabricated using modified (K_0.5Na_0.5)(Nb_0.9Ta_0.1)O₃ ceramics. Impedance and voltage gain characteristics were investigated of the transformer and preliminary research on the driver circuit was developed. The maximum step-up ratio more than 42 with no load condition has been obtained. It suggests that this system is a promising candidate for the lead-free piezoelectric transformer applications.更多还原