由同时电荷转移和极地-非极地转换引起的增强负热膨胀
Takumi Nishikubo1, Yuki Sakai1,2, Kengo Oka3
1Laboratory for Materials and Structures , Tokyo Institute of Technology , 4259 Nagatsuta, Midori-ku , Yokohama , Kanagawa 226-8503 , Japan.
Journal of the American Chemical Society
|November 19, 2019
概括
由于电荷转移和相位转换,在氧化铁中观察到负热膨胀. 在BiNi1-xFexO3的新发现提供了新的材料可能性.
科学领域:
- 材料科学
- 固态化学
- 晶体学
背景情况:
- 负热膨胀 (NTE) 是一种材料在加热时收缩的特性.
- 了解NTE背后的机制对于开发先进的功能材料至关重要.
- 基于的氧化物以其多样化的结构和电子性质而闻名.
研究的目的:
- 研究BiNi1-xFexO3中的负热膨胀的发生和机制.
- 探索组合,结构和热膨胀特性之间的关系.
- 在这种材料系统中确定驱动NTE的同时机制.
主要方法:
- 具有不同铁含量的BiNi1-xFexO3化合物的合成 (0.25 ≤ x ≤ 0.5).
- 用X射线衍射 (XRD) 和温度依赖的结构分析来确定晶体结构和相位过渡.
- 分析电荷分布和电子状态.
主要成果:
- 第一次观察BiNi1-xFexO3 (0.25 ≤ x ≤ 0.5) 中的NTE,由同时的电荷转移和极性-非极性转换驱动.
- 确定具有特定电荷分布的低温极相 (空间组R3c) (Bi3+/Bi5+/Ni2+/Fe3+).
- 由于降低的Ni2+而加热后的体积减少随着x的增加而减少,而独立于成分的~2%的体积减少与极地-非极地转换有关.
结论:
- 同时的电荷转移 (Bi5+-Ni2+) 和极性-非极性转换是BiNi1-xFexO3中的NTE的关键机制.
- 来自电荷转移的NTE的程度取决于组合,而相位过渡的贡献则独立于组合.
- 这项研究揭示了设计具有定制负热膨胀特性的材料的新途径.
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