In materials science, intentional doping has been widely used to improve the properties of a variety of materials. However, such an approach is not yet exploited in the fast-growing field of electrocaloric materials, which represent a serious alternative for next-generation cooling systems. Here we demonstrate with ${\mathrm{Ba}}_{0.9}{\mathrm{Sr}}_{0.1}{\mathrm{Hf}}_{0.1}{\mathrm{Ti}}_{0.9}{\mathrm{O}}_3$, an ecofriendly ferroelectric material, that doping with 2% of $\mathrm{Cu}$ introduces defect dipoles into the ferroelectric matrix and results in (i) enhancement of the adiabatic temperature change ΔT by up to 54% while maintaining performance after a large number (up to ${10}^4$) of electric field cycles, (ii) suppression of the parasitic irreversibility of ΔT between on-field and off-field states, and (iii) an alternative design of refrigeration cycle with a prepoled sample, allowing a two-field-step process showing both conventional (ΔT > 0) and inverse (ΔT < 0) responses when the field is sequentially varied. We also demonstrate that doping significantly increases the energy storage density (by up to 72%). The defect engineering approach therefore offers a path for designing ferroelectrics with improved electrocaloric performances. Beyond ferroelectrics, this strategy could also be promising in other solid-state caloric materials (magnetocalorics, elastocalorics, etc.).

中文翻译：

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掺杂引起的极性缺陷改善Ba0.9Sr0.1Hf0.1Ti0.9O3的电热性能

在材料科学中，有意掺杂已被广泛用于改善各种材料的性能。然而，这种方法尚未在快速发展的电热材料领域中得到利用，电热材料代表了下一代冷却系统的重要替代品。这里我们用${巴}_{0.9}{锶}_{0.1}{\mathrm{高频}}_{0.1}{钛}_{0.9}{\mathrm{哦}}_3$, 一种环保铁电材料, 掺杂 2% $铜$将缺陷偶极子引入铁电矩阵并导致 (i) 绝热温度变化 Δ T增强高达 54%，同时在大量（高达${10}^4$）电场周期，（ⅱ）Δ的寄生不可逆转抑制Ť之间上-field和关闭-field状态，和（iii）冷冻循环的替代设计与prepoled样品，允许两字段步骤的过程显示了当场 顺序变化时的常规 (Δ T  > 0) 和逆 (Δ T < 0) 响应。我们还证明掺杂显着增加了能量存储密度（高达 72%）。因此，缺陷工程方法为设计具有改进电热性能的铁电体提供了途径。除了铁电体，这种策略在其他固态热材料（磁热、弹性热等）中也很有前景。