基于多相临界点准同型相界的高温无铅压电陶瓷的组成设计、制备与性能调控

To meet the urgent demand of high temperature piezoelectric materials and devices above 400℃, based on strong piezoelectricty at multi-phases point MPB, a new high temperature and high performance lead-free piezoelectric ceramic of BiFeO3-(Bi1/2Na1/2)TiO3- Ba(Sn,Ti)O3(BF-BNT-BST) with multi-phases point MPB will be disigned by MPB compositions theory calculating and experimental investigating. The correlation between compositions and structure and process and electrical properties will be investigated and design criteria of high temperature and high performance piezoelectric ceramic will be explored. The difference of singtering temperature of BF and BST components is decreased by adding BNT and two-step synthesis and the thermodynamics and kinetics mechanism of sintering will be investigaed. The low temperature sintering technique and process will be obtained by adding sintering aid and rapid liquid-phase sintering. The room-temperature conducting mechanism will be studied by the impedance spectroscopy and scanning tunneling spectroscopy. The electrical properties adjustment mechanisms and methods will be obtained by modificating of A-site and B-site substitution and trace rare-earth doping. The multi-phases point MPB of rhombohedral, tetragonal, orthorhombic and cubicphases(multi- MPB) will be built and three key problems including lead-free piezoelectric ceramics with high temperature and high performance, low temperature preparation and room-temperature conducting will be solved through above study. Through this project, some theoretical and practical references will be offered for exploring new high temperature high performance lead-free piezoelectric ceramics. This project is closely connected with mineral resources advantages in Guangxi and helps the sustainable and healthy development of mineral resources economy in west China.

针对400℃以上使用的高温压电材料和器件的迫切需求，基于多相临界点准同型相界(MPB)的强压电效应，通过理论计算与实验研究，构造具有多相临界点MPB的高温高性能BiFeO3-(Bi1/2Na1/2)TiO3-Ba(Sn,Ti)O3(BF-BNT-BST)压电陶瓷体系，从组成/结构/工艺/性能关系探索高温高性能的设计准则。通过添加BNT、结合分步合成降低BF与BST组元间巨大的烧结温差，添加低温烧结助剂，结合快速液相烧结，研究低温烧结机理，获得相应的低温制备技术。通过A位、B位取代以及微量稀土元素掺杂，结合交流阻抗谱与扫描隧道谱获得室温漏电机理及高温高性能的调控途径。通过研究构建出三方\四方\正交\立方多相相界(多个MPB)组成，解决高温高性能无铅化、制备、室温漏电流三个关键问题，为探索高温高性能无铅压电材料提供实验和理论参考。本项目紧密结合广西矿产资源优势，有利于广西经济可持续健康发展。

基于BiFeO3-BaTiO3（BF-BT）高温无铅压电陶瓷具有居里温度高（>500°C），退极化温度高（>450°C）、压电性能好（>160PC/N）、以及具有较低的烧结温度（<950°C）的特性,本研究的目的旨在进一步提高其性能、降低介电损耗以及降低烧结温度的研究，以实现其替代铅基压电陶瓷的目标，采用通过理论计算和实验研究，设计构造含多相临界点MPB的BiFeO3-(Bi1/2Na1/2)TiO3-Ba(Sn, Ti)O3 (BF-BNT-BST)陶瓷体系，研究组成-温度-相结构以及组成-结构-性能的关联，获得高温高性能无铅压电陶瓷组成的设计原理；通过BF-BNT与BNT-BST固溶体分开合成降低组元间的烧结温度差、添加低温烧结助剂，采用快速液相烧结，阐明烧结机理，获得相结构、微观结构与电性能可控的压电陶瓷及相应的低温制备技术。但是在研究过程中，发现，BaSnO3的添加未能获得多相临界点的MPB成分，同时，BaSnO3的烧结温度高达1400°C，使得陶瓷的烧结变得更困难，性能恶化，未能获得性能较好的陶瓷。添加中间相(Bi1/2Na1/2)TiO3期望降低烧结温度，虽然获得了烧结致密的陶瓷，但由于三相之间的相结构变化太复杂，也未能获得多相临界点成分的陶瓷，(Bi1/2Na1/2)TiO3的添加反而使得性能急剧下降，因此在后续的研究中采用直添加烧结助剂Li2CO3、CuO的研究，获得了较低烧结温度的致密压电陶瓷，但性能未能得到突破，仍保持在170PC/N左右，2017年研究了添加Cu作为烧结助剂的Bi（Zn0.5Ti0.5）O3掺杂的BF-BT陶瓷，获得了d33=188PC/N的压电陶瓷，但仍然未能突破200PC/N。2017年年底还做了在高压氧气氛下烧结的BF-BT陶瓷，但目前在研究中，未能获得系统结论。