Giant Mechanocaloric Effects in Fluorite-Structured Superionic Materials
Giant Mechanocaloric Effects in Fluorite-Structured Superionic Materials
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DOI：
10.1021/acs.nanolett.6b00422
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发表时间：
2016-05-01
期刊：
影响因子：
10.8
通讯作者：
Errandonea, Daniel
中科院分区：
文献类型：
--
作者：
Cazorla, Claudio;Errandonea, Daniel
当对机械材料绝热施加机械应力时，它们的温度会发生变化。因此，到目前为止，只有铁电体和超弹性金属合金被认为是在固态冷却应用中开发的潜在机械热化合物。在这里，我们展示了巨大的机械热效应发生在迄今为止被忽视的快速离子导体（FIC）中，这是一类多组分材料，其中在临界温度T-s以上，组成离子物种的迁移率会突然增加。利用第一性原理和分子动力学模拟，我们发现萤石结构FIC的超离子跃迁，其特征是10(2)JK(-1) kg（-1）数量级的大熵增加，可以通过静水、双轴或单轴应力进行外部调谐。特别是，由于Frenkel对缺陷的形成能随之下降，通过施加适度的拉伸应力，T-s可以降低几百度。我们预测两种典型的萤石结构FIC CaF2和PbF2在临界点附近的绝热温度变化分别为10(2)和10(1)K。这项工作主张FIC构成了一个新的机械能材料家族，在未来的固态制冷应用中显示出巨大的希望。
Mechanocaloric materials experience a change in temperature when a mechanical stress is applied on them adiabatically. Thus, far, only ferroelectrics and superelastic metallic alloys have been considered as potential mechanocaloric compounds to be exploited in solid-state cooling applications. Here we show that giant mechanocaloric effects occur in hitherto overlooked fast ion conductors (FIC), a class of multicomponent materials in which above a critical temperature, T-s, a constituent ionic species undergoes a sudden increase in mobility. Using first-principles and molecular dynamics simulations, we found that the superionic transition in fluorite-structured FIC, which is characterized by a large entropy increase of the order of 10(2) JK(-1) kg(-1), can be externally tuned with hydrostatic, biaxial, or uniaxial stresses. In particular, T-s can be reduced several hundreds of degrees through the application of moderate tensile stresses due to the concomitant drop in the formation energy of Frenkel pair defects. We predict that the adiabatic temperature change in CaF2 and PbF2, two archetypal fluorite-structured FIC, close to their critical points are of the order of 10(2) and 10(1) K, respectively. This work advocates that FIC constitute a new family of mechanocaloric materials showing great promise for prospective solid-state refrigeration applications.