应力诱导钙钛矿型反铁电薄膜巨电卡效应的研究

The electrocaloric effect (ECE) has attracted a great deal of attention because it may provide a very efficient means to realize solid-state cooling devices for a broad range of applications such as on-chip cooling and temperature regulations for electronic devices. However, ECE reported in previous studies are small to be of practical use. On the other hand, the antiferroelectric to ferroelectric phase transition occurring in the antiferroelectric materials is usually accompanied by a large volume change. Inversely, an external strain/stress can also effectively change the critical field of phase transition. Therefore, a novel structure, antiferroelectric pervoskite film grown on single crystalline BaTiO3 substrate, is proposed and fabricated to study the enhanced ECE, which may be due to the strain resulting from the BTO phase transition.The effect of tensile/compressive strain on the ECE could be achieved via research of antiferroelectric films grown on different types of BTO ferroelectric domains. The sharp ECE work range would be broadened by increasing microstructure inhomogeneity of the BTO substrate. An interpretation is given to explain the giant ECE with that the variations of microstructure and ferroelectric domain in the antiferroelectric films. This program provides a method to enhance the ECE of the antiferroelectric films, which will give a guide to study the ECE.

基于电卡效应的铁电制冷技术在集成电路散热和工业冷藏等领域有广泛应用前景。目前电卡效应比较弱，不利于铁电制冷技术的发展和应用。反铁电材料在反铁电/铁电转变过程中伴随着大的体积变化，因此应力/应变能够影响反铁电材料的极化强度和临界电场。基于此本项目设计和构建钛酸钡(BaTiO3,BTO)单晶衬底外延生长反铁电薄膜的体系，利用BTO相变过程产生的应力/应变影响反铁电薄膜同一电场下极化强度提高反铁电薄膜的电卡效应。通过研究BTO不同类型铁电畴上反铁电薄膜电卡效应，获得张/拉应力对反铁电薄膜电卡效应的影响规律；在BTO衬底引入氧缺陷使BTO相变温区变宽，实现拓宽反铁电薄膜制冷工作温区；研究BTO相变前后反铁电薄膜晶体结构和铁电畴的变化，阐释反铁电薄膜巨电卡效应与其结构和铁电畴之间的关联。本项目提供了一种增强反铁电薄膜电卡效应的新方法和技术，为薄膜铁电致冷技术的研究提供一定指导意义。

目前电卡效应比较弱，不利于铁电制冷技术的发展和应用。本项目设计和构建钛酸钡(BaTiO3,BTO)单晶衬底外延生长反铁电薄膜的体系，利用BTO相变过程产生的应力/应变影响反铁电薄膜同一电场下极化强度提高反铁电薄膜的电卡效应。通过研究BTO不同类型铁电畴上反铁电薄膜电卡效应，获得张/拉应力对反铁电薄膜电卡效应的影响规律；在BTO衬底引入氧缺陷使BTO相变温区变宽，实现拓宽反铁电薄膜制冷工作温区；研究BTO相变前后反铁电薄膜晶体结构和铁电畴的变化，阐释反铁电薄膜巨电卡效应与其结构和铁电畴之间的关联 。提供了一种增强反铁电薄膜电卡效应的新方法和技术，为薄膜铁电致冷技术的研究提供一定指导意义。