PbTiO3-Based钙钛矿中铁电致伸缩和自旋交叉协同效应引起的巨负热膨胀
Giant Negative Thermal Expansion Induced by the Synergistic Effects of Ferroelectrostriction and Spin-Crossover in PbTiO3-Based Perovskites
摘要：
不寻常的负热膨胀（NTE）的发现提供了控制热膨胀的常见但非常期望的性质的机会，这不仅在科学兴趣中而且在实际应用中是有价值的。然而，大多数可用的NTE材料仅限于狭窄的温度范围，并且NTE效应通常通过各种改性来减弱。在此，我们报道了在宽温度范围（αV = -5.24 * 10-5 °C^-1，25-575 ° C）内发生的增强的NTE效应，并且这种NTE效应伴随着异常增强的四方性、大的自发极化和目前钙钛矿型铁电体（1-x）PbTiO 3-xBiCoO 3中的G型反铁磁有序。具体而言，对于0.5PbTiO3-0.5BiCoO3的组成，在700 °C的居里温度附近观察到约4.8%的广泛体积收缩，这代表了PbTiO 3基铁电体的最高水平。根据我们的实验和理论结果，巨NTE起源于铁电致伸缩和自旋交叉的钴晶格上的协同效应。实际的NTE机制与以前的功能NTE材料，其中的NTE是简单地耦合与一个排序，如电子，磁性，或铁电排序。本文的研究为理解NTE机理提供了新的思路，并证明了NTE可以通过不同的有序度进行合理的耦合，这将为大NTE材料的设计开辟一条新的途径。
英文摘要：
The discovery of unusual negative thermal expansion (NTE) provides the opportunity to control the common but much desired property of thermal expansion, which is valuable not only in scientific interests but also in practical applications. However, most of the available NTE materials are limited to a narrow temperature range, and the NTE effect is generally weakened by means of various modifications. Here, we report an enhanced NTE effect that occurs over a wide temperature range (αV = -5.24 * 10-5 °C^-1, 25-575 ° C), and this NTE effect is accompanied by an abnormal enhanced tetragonality, a large spontaneous polarization, and a G-type antiferromagnetic ordering in the present perovskite-type ferroelectric of (1-x)PbTiO3-xBiCoO3. Specifically, for the composition of 0.5PbTiO3-0.5BiCoO3, an extensive volumetric contraction of ~4.8 % has been observed near the Curie temperature of 700 °C, which represents the highest level in PbTiO3-based ferroelectrics. According to our experimental and theoretical results, the giant NTE originates from a synergistic effect of the ferroelectrostriction and spin-crossover of cobalt on the crystal lattice. The actual NTE mechanism is contrasted with previous functional NTE materials, in which the NTE is simply coupled with one ordering such as electronic, magnetic, or ferroelectric ordering. The present study sheds light on the understanding of NTE mechanisms and it attests that NTE could be simultaneouslycoupled with different orderings, which will pave a new way toward the design of large NTE materials.
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