高温钙钛矿结构铁电压电陶瓷新材料

High temperature piezoelectric sensors are strongly on-demanding for condition monitoring and acoustic nondestructive testing under those severe environments like in the fields of aerospace, nuclear power, oil-logging, petroleum chemical plants. To improve detection sensitivity and resolutions of piezoelectric sensors, it is most important to design novel piezoceramic materials with better performance than the present PbNb2O6 and Bi4Ti3O12 systems. Through data mining of material genome approach, BiFeO3, Bi(Zn1/2Ti1/2)O3 and (Pb,Ba)TiO3 ferroelectrics have been demonstrated to be the most potential end-members to construct high Curie temperature perovskite-structured solid solution with structural phase boundary benefitting for high piezoresponse. To quantitatively adjust Curie temperature and piezoresponse，to reduce residual tensile stress in ceramics are two basic problems in this project. Through this project, their crystallographic structure, structural phase transitions and piezoelectric properties with respect to various compositions near structural phase boundary of perovskites and microstructure grain size of BiFeO3-Bi(Zn1/2Ti1/2)O3-(Pb,Ba)TiO3 solid solution ceramics will be experimentally investigated, the quantitative relationships between structural phase transition temperature/piezoelectric constant and the genomes of material (including reduce mass of unit cell, grain size) will be tempted to establish, and then two kinds of piezoceramics will be optimized for high temperature piezoelectric sensors. High temperature acceleration sensors will be manufactured using those novel perovskite-type piezoceramics. This project will focus on the requirements of high temperature piezotronics and provides not only the theoretical fundaments of material design but also on-demanding candidates of piezoelectric sensors.

高温压电传感器在航空发动机、核电反应堆等国家重大工程在线监控方面有重大应用需求。提高传感器灵敏度和分辨率是重要方向。钙钛矿BiFeO3-Bi(Zn1/2Ti1/2)O3-(Pb,Ba)TiO3固溶体是构建结构相界、居里温度Tc>500oC、比目前商用的类钙钛矿偏铌酸铅和钛酸铋具有更高压电响应的铁电陶瓷新材料。居里温度与压电响应的量化调控关系、陶瓷材料残余张应力的消降是研发高性能高温钙钛矿压电陶瓷新材料的基本问题。本项目将对该钙钛矿铁电陶瓷材料的晶体结构、结构相变、压电性能等物理性质与组分、晶粒尺寸的构效关系深入研究，建立材料组成、晶粒尺寸等因素对相变温度、压电响应和热膨胀系数等物性的量化调控规律，优化开发两类高温压电陶瓷新材料，研制高温压电加速度传感器。本项目紧密围绕高温压电子学应用需求、研究铁电压电陶瓷材料的新设计原理，不仅为新材料研发提供理论基础、而且为高灵敏高温传感器提供新材料选项。

先进制造和智能制造的快速发展要求缩短新材料研发周期。材料研发包括发现、做出与做好三阶段；与试错式、筛选式不同，预测式按需设计具有最高的材料研发效率。材料的物理预测模型包括原子密堆系统的物理化学原理、变化规律以及预测目标三大要素。本项目采用数据科学范式与系统工程方法，通过对材料数据分层分类、通过构建选择具有化学组成与结构变化趋势的数字化系综描述符，小数据挖掘发现了钙钛矿氧化物铁电相变居里温度、自旋磁相变温度、禁带宽度、原胞体积等物性参数与μ×r_A/r_B（μ、r_A和r_B分别为元胞的约合质量、A位和B位离子半径）描述符之间的因果量化关系，首次实现了在统一标度下描述不同钙钛矿氧化物结构和物理性质；由此发现价电子和磁性离子内层电子与氧离子的轨道杂化程度都是μ×r_A/r_B描述符的函数、二者具有不同的变化趋势，不同的铁性相变温度对应不同的轨道杂化强度突变临界点；由此发现钙钛矿氧化物的铁电序和铁弹序都是原子系统体积失配导致的集体效应，由与原子大小和质量关联的化学压以及与价电子动态电负性关联的化学键共同决定；由此发现B位离子d0电子组态并不是铁电性产生的必要条件、而是强绝缘性铁电体的必要条件。基于这些因果关系与规律，建立了高温压电陶瓷、铁电和铁磁半导体等钙钛矿材料化学组成逆向设计的物理模型。基于d_33与ε_33间的量化关系，压电性能探索分为介电性质探索和压电响应验证两步进行，由此确认了残余张应力对BF-BZT-PBT铁电陶瓷极化处理的影响规律，初步获得了与商用偏铌酸铅和钛酸铋压电陶瓷工作温度相当的高性能钙钛矿型压电陶瓷。由于铁酸铋基固溶体钙钛矿的禁带宽度相对较窄、电阻率相对较低，在300oC以上温度热老化压电性能退化、尚不满足应用需求。虽然如此，在双钙钛矿氧化物中首次发现了室温铁磁半导体、发现了室温自旋阻挫磁性半导体，肯定地回答了《科学》杂志2005年提出的“是否存在室温铁磁半导体”问题。