论文标题
Mn $ _ {X} $ co $ _ {3-x} $ o $ $ $ $ _ {4} $ spinel薄膜
Jahn-Teller-driven Phase Segregation in Mn$_{x}$Co$_{3-x}$O$_{4}$ Spinel Thin Films
论文作者
论文摘要
长期以来，探索了由土壤丰富的Mn和CO组成的过渡金属尖晶石氧化物，以用于催化反应和能量储存。但是，由于样品制备的差异和材料的最终结构特性，对功能特性的理解可能具有挑战性。外延薄膜合成提供了一种新型的方法，可以生产精确控制的材料，以探索文献中报道的变化。在这项工作中，Mn $ _ {x} $ co $ _ {3-x} $ o $ $ _ {4} $样品从x = 0到x = 1.28合成了通过分子束的外交合成，并表征旨在开发材料属性映射作为stochiChiotry的函数。通过原位X射线光电光谱，X射线衍射，扫描透射电子显微镜和极化的K边缘X射线吸收光谱表征膜。发现该范围内的Mn阳离子与巨尖晶石结构一致。样品在很大程度上显示了混合Mn $^{3+} $和Mn $^{4+} $字符，具有相位分离趋势随着Mn含量增加并增加Mn $^{3+} $正式费用的证据。相位分离可能是由于与Mn $^{4+} $和Jahn-Teller Active Mn $^{3+} $ contahedra相关的立方和四方晶体结构之间的结构不兼容。我们的结果有助于解释这些有希望的可再生能源技术的有希望的材料中报告的差异。
Transition metal spinel oxides comprised of Earth-abundant Mn and Co have long been explored for their use in catalytic reactions and energy storage. However, understanding of functional properties can be challenging due to differences in sample preparation and the ultimate structural properties of the materials. Epitaxial thin film synthesis provides a novel means of producing precisely-controlled materials to explore the variations reported in the literature. In this work, Mn$_{x}$Co$_{3-x}$O$_{4}$ samples from x = 0 to x = 1.28 were synthesized through molecular beam epitaxy and characterized to develop a material properties map as a function of stoichiometry. Films were characterized via in situ X-ray photoelectron spectroscopy, X-ray diffraction, scanning transmission electron microscopy, and polarized K-edge X-ray absorption spectroscopy. Mn cations within this range were found to be octahedrally coordinated, in line with an inverse spinel structure. Samples largely show mixed Mn$^{3+}$ and Mn$^{4+}$ character with evidence of phase segregation tendencies with increasing Mn content and increasing Mn$^{3+}$ formal charge. Phase segregation may occur due to structural incompatibility between cubic and tetragonal crystal structures associated with Mn$^{4+}$ and Jahn-Teller active Mn$^{3+}$ octahedra, respectively. Our results help to explain the reported differences across samples in these promising materials for renewable energy technologies.
