钛酸铋钠基陶瓷的多功能特性调控、弛豫行为演变及构效关系研究

The exploration of lead-free functional electrical materials is one of the most challenging tasks. As the performance of the ferroelectric, dielectric, piezoelectric, energy storage, strain properties of sodium bismuth titanate-based ceramics is much lower than that of lead-based materials and there is no agreed final verdict on the structural origin of each functional electrical response, from the new perspective of the coexistence and transition of multifunction, the new route of lead-free functional ceramics replacing lead-based materials as well as the structural origin of the electrical function response will be investigated. By doping the ions at A sites, B sites of lattices in sodium bismuth titanate-based ceramics and combining with different components and functional structure units, the composite gradient and corresponding structure and composite structure will be modified. And the long-range order ferroelectric state will change from an antiferroelectric/nonergodic relaxation state to an ergodic relaxation ferroelectric phase, and finally switch to nearly paraelectric phase. The functional electrical response and transition at different ferroelectric states will be deeply investigated. By analyzing the evolution between different electrical function responses and its crystal structure, domain structure, polar micro-regions and chemical micro-regions, the multi-level and multi-scale structural features of the multifunctional responses will be explored, the structure-property relationships and multifunctional transition will also be established, and the structural origin of different electrical function responses will be clarified. Based on the above results, the ceramic-based devices with multifunctional properties will be studied. The results obtained in this project will also pave the way for lead-free functional materials replacing lead-based materials, and broaden and deepen the understanding of the electrical function response.

探索无铅电功能材料是最具挑战性的课题之一，针对钛酸铋钠基陶瓷的铁电、介电、压电、储能、应变等电功能响应还远低于铅基材料，以及每种电功能响应的结构来源尚无统一定论，从多功能特性共存及转变的新视角，研究无铅功能陶瓷取代铅基材料的新路线，以及电功能响应的结构起源。通过钛酸铋钠基陶瓷A位、B位离子掺杂，结合不同组元及功能结构单元的复合方式，调控功能单元组成梯度与结构以及复合结构，调控长程有序铁电态经由反铁电/非遍历弛豫态，转变为遍历弛豫铁电相，最后转变为近顺电相，研究不同铁电态的电功能响应及转变行为。分析晶体结构、电畴结构、极性微区和化学微区与不同电功能响应的演变，探讨多功能响应的多层次、多尺度结构特征，建立多功能响应及转变的构效关系，阐明不同电功能响应的结构来源。在此基础上，研制具有多功能性能的陶瓷基器件。研究结果可为无铅功能材料取代铅基材料开辟一条新的路径，拓宽与加深电功能响应内涵的深入认识。

铁电材料丰富的铁电、压电、介电、储能、应变等物理性能获得了广泛探索和应用，设计面向智能化和信息化等多功能集成的铁电材料与器件是科学前沿问题。从多功能特性共存及转变的新视角研究铁电陶瓷及电功能响应的结构起源。本申请从钛酸铋钠（BNT）基陶瓷的组成设计与制备入手，系统开展了BNT基陶瓷的电学多功能及演变与结构之间的应用基础研究工作。组分设计上，一方面采用钛酸钡（BT）、钛酸铋钾（BKT）与BNT构建铁电固溶体，再通过单离子（La、Sm、Sr）、二元（(Mn1/3Nb2/3)4+、(Mg1/3Nb2/3)4+、(Nd0.5Ta0.5)4+、(W0.5Mg0.5)4+、(Yb0.5Nb0.5)4+、(Lu0.5Nb0.5)4+、(Sr1/3Nb2/3)4+等）及三元（(Fe1/4Sc1/4Nb1/2)4+）复合离子改性，可以实现铁电态到反/类反铁电态、驰豫铁电态的转变，其铁电、介电、储能、应变等产生多个电学功能的演变，铁电态受组分的调控性较强；另一方面，采用反铁电组元Cs2Nb4O11和AgTa0.15Nb0.85O3，线性电介质Sr0.7Ca0.3TiO3对BNT-BT、BNT-BKT进行铁电态的调控，获得了储能与应变性能的提升。组分设计上还研究了钪酸铋（BS）与BNT、BT构建的固溶体实现了铁电态和多种电学功能的调控，以及对铌酸钾钠（KNN）固溶第二组元降低结构对称性提高可见光与红外波段的透光率、兼顾其铁电性和介电性能。工艺研究表明，烧结工艺（传统一步方式、两步烧结）、粉体配制方式（一步合成原料粉，单独合成原料粉再混合）对BNT基陶瓷的晶粒尺寸结构和压电、储能和应变性能产生较大的影响。探索了组分-铁电态、铁电态-电学多功能特性之间的演变规律，研究发现组分存在临界点，该临界点引起铁电态存在临界相变或共存，从而在临界点处产生多个优异的电学功能，如巨电致应变与高储能密度共存，铁电性、可见光透光性与介电稳定性共存，低场与高场压电共存。研究成果在国内外期刊发表学术论文30篇；申请专利6件，授权2件；培养10名硕士研究生。研究成果在相关学术会议和交流中以分组汇报、墙报展示等进行了介绍。负责人参与发起成立了电子元器件关键材料与技术专委会，并担任副秘书长。项目的研究结果对促进基于BNT陶瓷的新型多功能器件的开发具有一定的理论指导意义和实验基础。