钛酸铋钠基铁电固溶体的高极性可逆相变构建及窄滞后巨应变与高效储能特性调控

Due to serious harm to the ecological environment of lead based materials and inferior comprehensive performance of lead-free ferroelectric materials compared with lead-based counterpart, developing high performance lead-free materials would be demanded urgently. It is well known that Bi1/2Na1/2TiO3(BNT) based ceramics display ferroelectric phase transition with both ferroelectric shift and oxygen octahedral tilting. Three categories d0 transition metals with strong, moderateand weak out-of-center distorter will be selected as modifier. The effect of d0 transition metals on long range ferroelectric-intermediate or short range polar transition, stronger polar octahedral distortion and dynamic Jahn-Teller effect with induced orientational contribution to the polarization and electrostriction will be investigated. The synergistic action of above three categories polar phase transition with low hysteresis giant strain and efficient energy storage behaviors will be explored. Likewise, the competing and coupling between polar phase transition and octahedral tilting, and the mechanism of ferroelectric shift strain along with rotostriction will be studied. Long-period modulation bridging the competing displacement ferroelectric and tilting polar state will be constructed by designing the modulation structure unit. The tailoring methods and structure-properties relationship between displacement polarization combining with rotopolarization and giant strain and efficient energy storage will be obtained.By utilizing multiple-polarization and strain, the bottlenecks of reducing ferroelectric distortion and octhedral tilting surpressing ferroelectricity resulted from ferroelectric-realxor transition by conventional modification methods will be broken. Based on the above studies, new thought, method and theoretical direction for designing and preparation of high-performance lead-freeferroelectric ceramics will be proposed.

在减少铅基材料对生态环境的严重危害以及无铅铁电材料综合性能远远不及铅基材料的迫切要求下，基于窄滞后巨应变与高效储能来源于高极性可逆相变的前提，针对Bi1/2Na1/2TiO3基陶瓷具有离子位移和氧八面体旋转两种铁电相变类型，研究多种极性的协同作用来获得窄滞后巨应变与高效储能的途径及机理。引入强/中/弱三类畸变能力的d0过渡族离子，研究长程铁电相向中/短程极性相的转变、极性畸变增强行为、Jahn-Teller效应及诱导的极性有序排列与电致伸缩效应，探索三类极性相变协同作用及窄滞后巨应变与高效储能行为。通过构建长周期调制结构来桥接相互竞争的位移与八面体旋转极性模式，研究极性相变与旋转极化的竞争与耦合，获得位移极化与旋转极化的叠加及巨应变与储能的构效关系及调控途径。项目利用多种极性与应变叠加，以期打破八面体旋转抑制铁电性与改性导致铁电畸变弱化的瓶颈，为高性能无铅铁电陶瓷的设计提供新的思路与方法。

钛酸铋钠基无铅压电材料由于其特殊的结构和相变特征，应用领域包括如制动器、高温电容器、储能以及和电卡制冷等方面。通过掺杂、取代以及与其他具有铁电性的材料形成固溶体等，使得 BNT 基材料在很多方面性能都有了很大的进展，但BNT 目前仍存在如矫顽场较大、难以极化、漏电流较大、去极化温度Td 较低等问题。本项目利用过渡族金属离子对氧八面体畸变的调控效应，在BNT基陶瓷引入异价离子、同价离子单掺杂及复合离子掺杂，研究了掺杂BNT基陶瓷的物相结构、介电、铁电、储能密度等性能。通过掺杂产生随机场或随机应变，破坏长程铁电有序，诱导铁电-弛豫铁电相变，获得窄滞后巨应变及高效储能特性。通过第一性原理计算研究了不同元素掺杂对氧八面体畸变的影响，探索过渡族离子的增强极性相变与Jahn-Teller效应对可逆极性相变与电致伸缩效应的影响，结合微观结构、介电、铁电性能、应变响应和储能特性等实验，对长程铁电-极性弛豫相变行为及相应微观结构演化的影响与相互关联。项目利用不同畸变类型的离子掺杂诱导长程铁电向弛豫极性相转变过程，产生场致巨应变行为，在BNT-BT-xNZ 陶瓷实现高场巨应变S=0.72%，Smax/Emax=1200 pm/V等优异性能。.项目结果将为新型无铅压电材料的设计与实际应用、压电材料的结构和性能优化提供新的思路、方法和理论指导，将拓宽和加深对压电效应的微观来源的认识。研究结果受到国内外同行认可，目前发表11篇论文，其中SCI 收录 10 篇，授权实用新型专利2件，培养硕士4名。