通过钙掺杂调节铅钪钽的电热效应
Tunable electrocaloric effect in lead scandium tantalate through calcium doping
AI总结：
研究通过钙掺杂调控铅钪钽的相变，实现电热效应的精确调节，发现不同掺杂浓度下相变温度变化，并展示其在低温范围内的应用潜力。
摘要：
最先进的电制冷原型依赖于铁电铅钪钽（PbSc0.5Ta0.5O3，PST）的常规电热效应，其峰值接近室温。本文表明，高有序PST中A位钙掺杂会改变其相变并使电热响应可调。相变温度根据Ca浓度降至258 K或升至319 K。在电场下的热力学测量、电极化环和压电响应力显微镜揭示了Ca≥2%时出现的中间反铁电相。这些结果由第一性原理计算支持。我们观察到Ca≤2%时有常规电热效应，而更高掺杂（≥2%）时出现反向电热效应。在110 kV cm⁻¹电场下，Ca掺杂PST在263 K至353 K范围内产生2 K的绝热温度变化。此类Ca掺杂PST化合物可用于扩展PST在水冻结点以下的温度范围。我们的结果提供了一条通往扩展操作范围的电制冷设备的路径。
英文摘要：
State-of-the-art electrocaloric cooling prototypes rely on the conventional electrocaloric effect of ferroelectric lead scandium tantalate (PbSc0.5Ta0.5O3, PST), which peaks near room temperature. Here, we demonstrate that A-site calcium doping in highly ordered PST modifies its phase transitions and enables precise tuning of the electrocaloric response. The transition temperature shifts down to 258 K and up to 319 K, depending on Ca concentration. Calorimetry under electric field, electrical polarization loops, and piezoresponse force microscopy reveal the emergence of an intermediate antiferroelectric phase stabilized for Ca $\geq$ 2\%. These results are supported by first-principles calculations. We observe a conventional electrocaloric effect for Ca $\leq$ 2\% and an inverse electrocaloric effect at higher doping ($\geq$ 2\%). Under an applied field of 110 kV cm$^{-1}$, Ca-doped PST exhibits an adiabatic temperature change of 2 K over a range from 263 K to 353 K. Such Ca-doped PST compounds could be used to expand the temperature range of PST below the freezing point of water. Our results offer a pathway to cascaded electrocaloric cooling devices with extended operating spans.
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