Topotactic Transition: A Promising Opportunity for Creating New Oxides

Abstract

Topotactic transition is a structural phase change in a matrix crystal lattice mediated by the ordered loss/gain and rearrangement of atoms, leading to unusual coordination environments and metal atoms with rare valent states. As early as in 1990s, low temperature hydride reduction is utilized to realize the topotactic transition. Since then, topological transformations are developed via multiple approaches. Especially, the recent discovery of the Ni‐based superconductivity in infinite‐layer nickelates has greatly boosted the topotactic transition mean to synthesizing new oxides for exploring exotic functional properties. In this review, a detailed and generalized introduction is provided to oxygen‐related topotactic transition. The main body of the review includes four parts: the structure‐facilitated effects, the mechanism of the topotactic transition, some examples of topotactic transition methods adopted in different metal oxides (V, Mn, Fe, Co, Ni) and the related applications. This study is to provide timely and thorough strategies to successfully realize topotactic transitions for researchers who are eager to create new oxide phases or new oxide materials with desired functions.

Synthesis of thin film infinite-layer nickelates by atomic hydrogen reduction: Clarifying the role of the capping layer

“…58 We find that exposure to an atomic hydrogen flux of ∼2 × 10 15 at./cm 2 /s for <15 min at sample temperatures between 250 and 300 ○ C is sufficient to transform ∼7.5 nm thick perovskite films to the IL phase, a much shorter exposure compared to traditional CaH 2 annealing. 59 We further demonstrate that this procedure produces IL films with high structural quality, smooth surfaces, and favorable electrical characteristics. Finally, we leverage the compatibility of this technique with in situ probes, namely, RHEED, to study the effects of atomic and molecular hydrogen exposure on the film surface and the resulting impact on the reduction process.…”

“…These measurements indicate that care must be taken when investigating the details of the MIT in highly strained nickelates, as well as unveiling a potentially uncontrolled variable in nickelate reduction experiments. Topotactically reduced oxides have proven to be a rich, expanding field for the investigation of novel ground states in quantum materials; 1,23,35,59,[75][76][77][78][79][80][81][82] we put forth atomic hydrogen reduction as a highly tunable process for synthesizing reduced oxides of high quality. The vacuum compatibility of this technique both expands the range of experiments that may be performed on reduced films and enables in situ and operando studies of the reduction process itself.…”

Oxygen Storage Property and Catalytic Performance of Ti-Doped FeNbO4

“…Consequently, even after the release of the oxide ions, the nonreducible A-site cations act as pillars that prevent the collapse of the close-packed structure. Therefore, these perovskite-related oxides can release and store lattice oxygen topotactically, and many of them have been reported as excellent OSMs. ,− …”