IF 9.4 1区 材料科学 Q1 CHEMISTRY, PHYSICAL
Hao-Cheng Thong, Fang-Zhou Yao, Xian-Xian Cai, Ze Xu, Mao-Hua Zhang, Huazhang Zhang, Ben Xu, Yan Wei, Shi-Dong Wang, Ke Wang
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引用次数: 0

摘要

铁电体的功能通常受到其居里温度的限制,超过居里温度就会发生去极化。锂(Li)是实验中唯一已知的能提高铁电铌酸盐基包晶石居里温度的替代物,但其机理仍未解决。本文采用第一原理密度泛函理论研究了锂取代 KNbO3 的独特现象。理论计算表明,锂在包晶石 A 位的取代引入了压缩化学压力,降低了 Nb-O 杂化和相关的铁电不稳定性。然而,锂阳离子的大偏心位移弥补了这种降低,并进一步增强了软极性模式,从而提高了居里温度。此外,根据预测,锂取代后的四方相比正方相稳定,这合理地解释了正方相到四方相转变温度降低的实验观察结果。最后,还发现了一种可蜕变的反相极性状态,在这种状态下,锂阳离子与铌阳离子相对位移,这也可能导致相变温度的变化。这些发现为研究铁电材料居里温度增强的原子尺度机制提供了重要见解,并为设计具有更好热稳定性和功能性能的先进铁电材料铺平了道路。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

Increased Curie temperature in lithium substituted ferroelectric niobate perovskite via soft polar mode enhancement

Increased Curie temperature in lithium substituted ferroelectric niobate perovskite via soft polar mode enhancement

The functionality of ferroelectrics is often constrained by their Curie temperature, above which depolarization occurs. Lithium (Li) is the only experimentally known substitute that can increase the Curie temperature in ferroelectric niobate-based perovskites, yet the mechanism remains unresolved. Here, the unique phenomenon in Li-substituted KNbO3 is investigated using first-principles density functional theory. Theoretical calculations show that Li substitution at the A-site of perovskite introduces compressive chemical pressure, reducing Nb–O hybridization and associated ferroelectric instability. However, the large off-center displacement of the Li cation compensates for this reduction and further enhances the soft polar mode, thereby raising the Curie temperature. In addition, the stability of the tetragonal phase over the orthorhombic phase is predicted upon Li substitution, which reasonably explains the experimental observation of a decreased orthorhombic-to-tetragonal phase transition temperature. Finally, a metastable anti-phase polar state in which the Li cation displaces oppositely to the Nb cation is revealed, which could also contribute to the variation of phase transition temperatures. These findings provide critical insights into the atomic-scale mechanisms governing Curie temperature enhancement in ferroelectrics and pave the way for designing advanced ferroelectric materials with improved thermal stability and functional performance.

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来源期刊
npj Computational Materials
npj Computational Materials Mathematics-Modeling and Simulation
CiteScore
15.30
自引率
5.20%
发文量
229
审稿时长
6 weeks
期刊介绍: npj Computational Materials is a high-quality open access journal from Nature Research that publishes research papers applying computational approaches for the design of new materials and enhancing our understanding of existing ones. The journal also welcomes papers on new computational techniques and the refinement of current approaches that support these aims, as well as experimental papers that complement computational findings. Some key features of npj Computational Materials include a 2-year impact factor of 12.241 (2021), article downloads of 1,138,590 (2021), and a fast turnaround time of 11 days from submission to the first editorial decision. The journal is indexed in various databases and services, including Chemical Abstracts Service (ACS), Astrophysics Data System (ADS), Current Contents/Physical, Chemical and Earth Sciences, Journal Citation Reports/Science Edition, SCOPUS, EI Compendex, INSPEC, Google Scholar, SCImago, DOAJ, CNKI, and Science Citation Index Expanded (SCIE), among others.
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