Dai Changshun, Li Feng, Long Mingsheng, Tan Daniel Q, Shan Lei, Wang Chunchang, Wang Jianli, Cheng Zhenxiang
Information Materials and Intelligent Sensing Laboratory of Anhui Province, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, China.
Leibniz International Joint Research Center of Materials Sciences of Anhui Province, Anhui University, Hefei 230601, China.
ACS Appl Mater Interfaces. 2024 Aug 14;16(32):42435-42447. doi: 10.1021/acsami.4c06592. Epub 2024 Jul 30.
High-performance electrocaloric materials are essential for the development of solid-state cooling technologies; however, the contradiction of the electrocaloric effect (ECE) and temperature span in ferroelectrics frustrates practical applications. In this work, through modulating oxygen octahedra distortion and short-range polar nanodomains with moderate coupling strength, an EC value of Δ ∼ 0.30 K with an ultrawide temperature span of 85 K is obtained in the = 0.04 composition [(0.88 - )NaNbO-0.12BaTiO-LiSbO ( = 0-0.06)]. The LiSbO dopant induces a -to- phase transition and intensifies the oxygen octahedra distortion degree, accompanied by the ferroelectric domain smashing into polar nanodomains. Also, LiSbO addition enhances the relaxation degree with a downshift of (ferroelectric-to-diffuse phase transition temperature) and (temperature of the maximal current density value), and is shifted to near room temperature with an absence of in = 0.04. Local energy barriers induced by oxygen octahedra distortion inhibit the phase transition in conjunction with activation of short-range polar order switching under thermal stimuli, which is the underlying mechanism for an excellent EC performance for = 0.04. This work not only clarifies that ferroelectrics with oxygen octahedra distortion and short-range polar order are expected to achieve remarkable EC performances but also provides a design strategy to seek emergent EC behaviors in complex oxygen-octahedra-distortion materials.
高性能电热材料对于固态冷却技术的发展至关重要；然而，铁电体中电热效应（ECE）与温度跨度之间的矛盾阻碍了其实际应用。在这项工作中，通过调节具有适度耦合强度的氧八面体畸变和短程极性纳米畴，在x = 0.04的[(0.88 - x)NaNbO₃ - 0.12BaTiO₃ - LiSbO₃（x = 0 - 0.06）]成分中获得了Δ ∼ 0.30 K的电热系数值以及85 K的超宽温度跨度。LiSbO₃掺杂剂诱导了从三方相到四方相的转变并增强了氧八面体的畸变程度，同时铁电畴破碎成极性纳米畴。此外，添加LiSbO₃提高了弛豫程度，使三方相到漫散相转变温度（Tₘ）和最大电流密度值温度（Tₚ）降低，并且在x = 0.04时Tₘ移至接近室温且不存在Tₚ。氧八面体畸变引起的局部能垒抑制了相变，同时热刺激下短程极性有序切换被激活，这是x = 0.04时具有优异电热性能的潜在机制。这项工作不仅阐明了具有氧八面体畸变和短程极性有序的铁电体有望实现显著的电热性能，还提供了一种在复杂的氧八面体畸变材料中寻求新兴电热行为的设计策略。
