Large Negative Thermal Expansion Induced by Synergistic Effects of Ferroelectrostriction and Spin Crossover in PbTiO3-Based Perovskites
Large Negative Thermal Expansion Induced by Synergistic Effects of Ferroelectrostriction and Spin Crossover in PbTiO3-Based Perovskites
复制标题
PbTiO3 基钙钛矿中铁电致伸缩和自旋交叉的协同效应引起的大负热膨胀
DOI：
10.1021/acs.chemmater.8b04266
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发表时间：
2019
影响因子：
8.6
通讯作者：
Chen Jun
中科院分区：
文献类型：
--
作者：
Pan Zhao;Chen Jun
不寻常的负热膨胀（NTE）的发现提供了控制常见但非常理想的热膨胀特性的机会，这不仅在科学兴趣上而且在实际应用中都很有价值。然而，大多数可用的NTE材料仅限于较窄的温度范围，并且NTE效应通常会因各种修饰而减弱。在这里，我们报告了在较宽的温度范围内（α̅V= -5.24 × 10–5°C–1, 25–575 °C）发生增强的 NTE 效应，并且这种 NTE 效应伴随着当前钙钛矿型铁电体 (1–x)PbTiO3–xBiCoO3 中异常增强的四方性、大的自发极化和 G 型反铁磁有序性。具体来说，对于 0.5PbTiO3–0.5BiCoO3 的成分，在 700 °C 的居里温度附近观察到了约 4.8% 的广泛体积收缩，这代表了 PbTiO3 基铁电体的最高水平。根据我们的实验和理论结果，大的NTE源于钴的铁电致伸缩和晶格上的自旋交叉的协同效应。实际的 NTE 机制与之前的功能性 NTE 材料形成对比，其中 NTE 简单地与一种排序（例如电子、磁性或铁电排序）耦合。本研究揭示了对 NTE 机制的理解，并证明 NTE 可以同时与不同的排序耦合，这将为大型 NTE 材料的设计开辟新的途径。
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 various modifications. Here, we report an enhanced NTE effect that occurs over a wide temperature range (α̅V= −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 large 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 simultaneously coupled with different orderings, which will pave a new way toward the design of large NTE materials.