节点文献
锆钛酸钡钙基弛豫铁电薄膜的制备及能量储存与电卡效应研究
Preparation and Study on Energy Storage and Electrocaloric Effect of BCZT-Based Relaxor Ferroelectric Thin Films
【作者】 何上恺;
【导师】 王宁章;
【作者基本信息】 广西大学 , 材料学, 2019, 硕士
【摘要】 铁电薄膜较其块体陶瓷材料具有更优的电学性能,在电容器储能、固态电卡制冷以及位移驱动器等领域中有着广泛的应用。在本文中,以Ba(Zr0.2Ti0.8)O3-(Ba0.7Ca0.3)TiO3体系的伪二元固溶体相图中的立方相、四方相和三方相三相共存成分点0.68BZT-0.32BCT(简写为纯BCZT)为基准,使用溶胶凝胶法制备了[(Ba0.904Ca0.096)0.9775+xLa0.015(Zr0.136Ti0.864)O3,x = 0.0075,0.075 and 0.15](简写为La-doped BCZT)介电弛豫薄膜电容器。系统研究了A位过量程度、底电极种类和顶电极大小对纯BCZT和La-doped BCZT薄膜的微观结构和储能性能的影响。此外,挑选出综合储能性能最为优异的La-doped BCZT(x=0.0075)薄膜(简写为BCLZT)与Pb0.8Ba0.2ZrO3薄膜(简写为PBZ)进行复合,制备了 BCLZT/PBZ多层薄膜,研究了底电极种类对BCLZT/PBZ多层薄膜的微观结构和电卡效应的影响。结果表明:(1)沉积在LaNiO3/Pt复合底电极上的La-doped BCZT(x = 0.0075)弛豫薄膜电容器具有大的储能密度值15.5 J/cm3,高的储能效率93.7%,同时具有良好的温度稳定性:储能密度在20℃~260℃范围内及储能效率在20℃~140℃范围内变化率都在5%以内。La-doped BCZT(x=0.0075)薄膜电容器优异的储能性能归功于三相共存点(Ba0.904Ca0.096)(Zr0.136Ti0.864)O3附近纳米团簇结构的多样性,和LaNiO3/Pt复合底电极的使用。顶电极面积与薄膜性能之间的关系表示,当沉积在LaNi03/Pt复合底电极的La-doped BCZT(x= 0.0075)薄膜的Pt顶电极面积高达约7.079 mm2时,薄膜的储能密度为0.7 J/cm3,效率高达约91.4%,并且其储能性能会随着顶电极质量的优化得到进一步提高。(2)沉积在Pt底电极和LaNi03/Pt复合底电极上BCLZT/PBZ多层薄膜均为纯的钙钛矿结构。LaNi03/Pt复合底电极的使用提高了BCLZT/PBZ多层薄膜的介电性能和电卡效应。当外加电场为756kV/cm时,沉积在Pt底电极和LaNi03/Pt复合底电极上BCLZT/PBZ多层薄膜在室温处的最大△T值分别为6.6K和20.4K。
【Abstract】 Ferroelectric thin films are widely used in dielectric storage capacitors,solid-state cooling devices and displacement devices due to the better electrical properties than bulk ceramic materials.In this paper,the three-phases(cubic,tetragonal and rhombohedral phases)coexisting component point 0.68BZT-0.32BCT(abbreviated as pure BCZT)in the phase diagram of pseudobinary ferroelectric system Ba(Zr0.2Ti0.8)O3-(Ba0.7Ca0.3)TiO3 was chosen to be the basic component of[(Ba0.904Ca0.096)0.9775+xLa0.015(Zr0.136Ti0.864)O3,x =0.0075,0.075 and 0.15](abbreviated as La-doped BCZT)dielectric relaxor thin film capacitors prepared by using a sol-gel method.The effects of A-site excess,type of bottom electrodes and the size of top electrodes on the microstructure and energy storage properties of pure BCZT and La-doped BCZT films were systematically investigated.Moreover,La-doped BCZT(x = 0.0075)(abbreviated as BCLZT)thin films possessing the best comprehensive energy storage performance and Pb0.8Ba0.2ZrO3(abbreviated as PBZ)thin films are composited to prepare BCLZT/PBZ multilayer thin films.The effects of different bottoms on the microstructure and electrocaloric effect of BCLZT/PBZ multilayer thin films were investigated.The results are as follows.(1)The large energy storage density(W~15.5 J/cm3),ultra-high efficiency(η~93.7%)and high thermal stability(the variation of both W from 20 0C to 260℃ and η from 20℃ to 140℃ is less than 5%)have been simultaneously achieved in the La-doped BCZT(x = 0.0075)lead-free relaxor ferroelectric thin film capacitors deposited on LaNiO3/Pt composite bottom electrodes.The good energy storage property of the La-doped BCZT(x = 0.0075)thin film capacitors is mainly ascribed to the diversity of the structure of the nano-clusters around the three-phases coexisting component point,as well as the ultra-high quality of thin film due to the utilization of the LaNiO3/Pt composite bottom electrode.The relationship between top electrode area and energy storage performance indicates that W value of the La-doped BCZT(x = 0.0075)deposited on LaNiO3/Pt composite electrode is 0.7 J/cm3,and the η value is still as high as 91.4%when the area of Pt top electrode has been increased to~7.079 mm2.Morever,Its energy storage performance will be further improved with the optimization of the top electrode quality.(2)Both the BCLZT/PBZ multilayer thin films deposited on the Pt and LaNiO3/Pt composite bottom electrodes exhibit the pure perovskite structures.In addition,the utilization of LaNiO3/Pt composite bottom improves the dielectric properties and electrocaloric of BCLZT/PBZ multilayer thin films.When the operation electric field is 756 kV/cm,the △T for BCLZT/PBZ multilayer thin films deposited on the Pt and LaNiO3/Pt composite bottom electrodes at room temperature are 6.6 K and 20.4 K,respectively.
【Key words】 BCZT; PBZ; Composite films; Sol-gel; Energy storage; Electrocaloric effect;