多相共存与弛豫特性对NaNbO3基材料电卡效应的协同调控

基于电卡效应的固态制冷器件具有小型化、集成化和高制冷效率等优点。NaNbO3基陶瓷因高极化强度和丰富的相转变特性而有望成为高性能的电卡材料。由于宽温区和高电卡效应之间相互制约，协同优化电卡效应及温度稳定性是实现电卡效应器件化的关键。因此，本项目拟设计多相共存NaNbO3基弛豫铁电材料，开展：1）阐明温度/组成对NaNbO3基材料结构演变与铁电-弛豫相转变的控制机理；2）构建多相共存NaNbO3基弛豫铁电材料并研究多相共存和弛豫特性对电卡效应的协同调控；3）揭示温度/组成-多相共存-弛豫特性-电畴/局域结构-电卡效应之间的相互联系，阐明多相共存NaNbO3基弛豫铁电材料的构效关系并勾勒宽温区、高电卡效应材料设计的理论图像。通过本项目的开展，我们旨在获得宽温区、高电卡效应的NaNbO3基弛豫铁电材料，并呈现协同优化电卡效应及温度稳定性的可行路径，为制备高性能的铁电制冷材料提供指导。

Solid–state cooling devices, which are based on electrocaloric effect (ECE), have advantages of miniaturizations, integrations and high cooling efficiency. NaNbO3–based ceramics are promising candidates to be high–performance EC materials as their high polarization and rich phase transitions. Since wide–span and high ECE are mutually restricted, synergistically optimizing ECE and temperature stability is the key to ECE devices. Therefore, this program will design NaNbO3–based relaxor ferroelectric ceramics with multiphase coexistence, thus explore: 1) determining the control mechanism of temperature/composition on structural evolution and ferroelectric–to–relaxor phase transition; 2) constructing multiphase–coexistence NaNbO3–based relaxor ferroelectric ceramics and explore the influence of multiphase coexistence and relaxor characteristic on modulation of ECE synergistically; 3) unravelling relationships among temperature/composition–multiphase coexistence–relaxor characteristic–domain/local structure–ECE, clarifying the structure–performance relationships in NaNbO3–based ferroelectric relaxor ceramics and delineating a theoretical image to design materials with wide–span and high ECE. Through developing this project, we expect to obtain NaNbO3–based ferroelectric relaxor ceramics with wide–span and high ECE, present a feasible route to synergistically optimizing ECE and temperature stability and provide a guidance to procure high–performance ferroelectric cooling materials.