Wang Le, Yang Zhenzhong, Bowden Mark E, Freeland John W, Sushko Peter V, Spurgeon Steven R, Matthews Bethany, Samarakoon Widitha S, Zhou Hua, Feng Zhenxing, Engelhard Mark H, Du Yingge, Chambers Scott A
Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, 99354, USA.
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, 99352, USA.
Adv Mater. 2020 Nov;32(45):e2005003. doi: 10.1002/adma.202005003. Epub 2020 Oct 2.
Creating new functionality in materials containing transition metals is predicated on the ability to control the associated charge states. For a given transition metal, there is an upper limit on valence that is not exceeded under normal conditions. Here, it is demonstrated that this limit of 3+ for Ni and Fe can be exceeded via synthesis of (SrNiO ) /(LaFeO ) superlattices by tuning n and m. The Goldschmidt tolerance constraints are lifted, and SrNi O with holes on adjacent O anions is stabilized as a perovskite at the single-unit-cell level (m = 1). Holding m = 1, spectroscopy reveals that the n = 1 superlattice contains Ni and Fe , whereas Ni and Fe are observed in the n = 5 superlattice. It is revealed that the B-site cation valences can be tuned by controlling the magnitude of the FeO octahedral rotations, which, in turn, determine the energy balance between Ni /Fe and Ni /Fe , thus controlling emergent electrical properties such as the band alignment and resulting hole confinement. This approach can be extended to other systems for synthesizing novel, metastable layered structures with new functionalities.
在含过渡金属的材料中创造新功能取决于控制相关电荷态的能力。对于给定的过渡金属，在正常条件下存在一个不被超过的价态上限。在此，通过调整n和m合成(SrNiO ) /(LaFeO )超晶格，证明了镍和铁的这种3 +的限制可以被突破。打破了戈尔德施密特容忍限制，具有相邻氧阴离子上有空穴的SrNi O在单胞水平（m = 1）上作为钙钛矿得以稳定。保持m = 1，光谱显示n = 1的超晶格包含Ni 和Fe ，而在n = 5的超晶格中观察到Ni 和Fe 。研究表明，可以通过控制FeO八面体旋转的幅度来调节B位阳离子价态，这反过来又决定了Ni /Fe 和Ni /Fe 之间的能量平衡，从而控制诸如能带排列和由此产生的空穴限制等新兴电学性质。这种方法可以扩展到其他系统，以合成具有新功能的新型亚稳层状结构。
