离子对缺陷调控无铅压电陶瓷及其对压电性能和温度稳定性的影响

BaTiO3 ceramics are mainly used as dielectric materials instead of piezoelectric materials because of the excellent dielectric properties and low piezoelectric properties. The previous studies have focused on the improvement of the piezoelectric properties of the ceramics to satisfy the requests of applications by doping method and fine grain effect, however, doping will lead to the decrease of the Curie temperature, and fine grains must be obtained to the preparation of fine powders and special sintering methods, which causes complex process and high price.The present study is put forward on the basis of the following reasons. On the one hand, the ceramics with high Curie temperature, good piezoelectric properties and temperature stability can be easily achieved using ordinary raw materials and conventional sintering method.On the other hand, it is always intriguing to research whether there is another appoach to obtain large piezoelectric properties except morphotropic phase boundary (MPB) or polymorphic phase transition (PPT). The materials studied in the present project are doped BaTiO3 and BiFeO3-BaTiO3 composite ceramics. The conditions of the formation and oriented distribution of A-A site ionic pairs will be analyzed in detail. By doping smaller acceptor and donor ions to substitute the neighboring A-sites in the lattice of ABO3-type perovskite, the A-A site defect dipoles (ionic pairs) can be constituted. The coupling behaviors and mechanisms of the oriented distribution of A-A site ionic pairs and polarization directions of ferroelectrics will be investigated. The origin of large piezoelectric response and high temperature stability indued by A-A site ionic pairs will be revealed. The influence of ionic-pair type, doping content and phase structure on the piezoelectric properties of the ceramics will be obtained. We expect that the results provided in the present study are significant for the enhancement of piezoelectric properties and helpful for the design of new-type lead-free piezoelectric ceramic materials.

钛酸钡陶瓷具有高介电、低压电性能，主要作为介电材料而不是压电材料来使用，以往研究主要利用掺杂改性和细晶效应改善压电性能以适应器件对其综合性能的要求，但掺杂易导致居里温度降低，细晶则需要精细粉体和特殊烧结使得工艺复杂成本较高。本项目的提出主要基于以下两点：一是利用普通原料和固相合成法获得居里温度高、压电性能优异、温度稳定性好的陶瓷；二是探索一个新的与准同型相变和多型性相变不同的大压电机制。本项目将以BaTiO3和BiFeO3-BaTiO3复合陶瓷为对象，拟采用施主受主共掺杂A位构建A-A位缺陷偶极子的离子对，探讨在钙钛矿陶瓷中A-A位离子对的形成条件及其取向分布，通过A-A位离子对取向控制与铁电体极化耦合行为与机制的研究，揭示A-A位离子对作用下陶瓷大压电响应及其高温度稳定性的起源，阐明离子对种类、掺杂含量、相结构等对陶瓷压电性能的影响规律，为优化陶瓷压电性能、设计新型压电材料提供依据。

钛酸钡(BaTiO3，BT)陶瓷由于具有良好的介电和铁电性能，被广泛应用于多层陶瓷电容器(MLCC)、PTC热敏电阻、铁电随机存储器、光学、热释电探测器等设备中。然而，BT陶瓷的实际应用仍旧受限于其相对较低的压电性能和较低的居里温度，因此在多数情况下，BT陶瓷主要是作为介电材料而不是作为压电材料来使用的。以往研究主要利用掺杂改性和细晶效应改善压电性能以适应器件对其综合性能的要求，但掺杂易导致居里温度降低，细晶则需要精细粉体和特殊烧结使得工艺复杂成本较高。本项目主要以BT和BiFeO3-BaTiO3（BFO-BT）陶瓷材料为基体，利用普通原料和固相合成法进行陶瓷材料的制备，采用施主受主共掺杂A位构建A-A位缺陷偶极子的离子对，探讨在钙钛矿陶瓷中A-A位离子对的形成条件及其取向分布，阐明离子对种类、掺杂含量、物相、微观组织结构等对陶瓷介电、铁电及压电性能的影响规律。对在T相区形成A-A位离子对的BT和BFO-BT压电陶瓷材料进行了比较系统的研究，结果发现，A-A位离子对不仅能够显著提高压电陶瓷的压电常数，而且还能够明显改善其压电常数的温度稳定性。在R相区，发现施主受主共掺杂下陶瓷材料的漏电性能有极大程度的改善，通过进一步优化BT和BFO含量以及A位共掺杂含量，能够获得居里温度高、压电性能优异、温度稳定性好的A位共掺杂BFO-BT压电陶瓷材料，为设计和优化具有ABO3钙钛矿型结构的铁电陶瓷提供了可资借鉴的方法和途径。通过对B位共掺杂BFO陶瓷的电学性能测试及漏电机理分析，结果发现，B位共掺杂能够有效的降低陶瓷介电损耗和漏电流，明显增强陶瓷的铁电性能，与纯BFO陶瓷相比，漏电流能够降低2~3个数量级。通过A-A位离子对取向控制与铁电体极化耦合行为与机制的研究，揭示A-A位离子对作用下陶瓷大压电响应及其高温度稳定性的起源，为优化陶瓷压电性能、设计新型压电材料提供依据。. 在本项目资助下，共发表SCI论文4篇，申请发明专利3项，已授权发明专利1项，参加学术及交流会议3次，并培养了1名博士研究生，2名硕士研究生。