Generalizing Metal-Assisted Topotactic Reduction in Complex Transition Metal Oxides

Topochemistry has emerged as a powerful technique for the synthesis of metastable oxide phases by selectively removing (or inserting) mobile species while preserving the structure of the host lattice [1]. These structural transformations enable host atoms to adopt unusual oxidation states and coordination environments, providing new methods to manipulate the electronic properties of oxide systems  [2]. Notably, these topochemical reactions have enabled the realization of superconductivity in rare-earth nickelates by reducing a perovskite precursor to the infinite-layer phase [3]. Topotactic reduction of transition metal oxides have often been achieved via reaction with gaseous hydrogen [4], and with metal hydrides [5]. However, recent work has demonstrated the use of metal-cap assisted reduction to be effective in producing superconducting nickelates  [6,7].  In this work, we investigate the critical parameters from metal-cap assisted reduction and generalize upon the use of this technique to synthesize and improve the quality of other oxide systems like infinite layer SrFeO₂ [8] and brownmillerite LaNiO_2.5 [9].  

References

[1]       M. A. Hayward, Semicond. Sci. Technol. 29, 064010 (2014).

[2]       Z. Meng et al., Adv Funct Materials 2305225 (2023).

[3]       D. Li et al., Nature 572, 624 (2019).

[4]       M. Crespin et al., Journal of Solid State Chemistry 178, 1326 (2005).

[5]       A. Ikeda, Physica C 4 (2014).

[6]       Zhang, Dongxin, et al. arXiv:2411.04896 (2024).

[7]       W. Wei et al., Sci. Adv. 9, eadh3327 (2023).

[8]       S. Inoue et al., Applied Physics Letters 92, 161911 (2008).

[9]       M. Kawai et al., Applied Physics Letters 94, 082102 (2009).