Résumé
Iron arsenide and selenide high temperature superconductors burst onto the scene unexpectedly in 2008. While the precise nature of the physics of these materials remains obscure, there are some chemical factors which enable control of the superconductivity in these compounds which are fairly clear. This talk will include descriptions of the soft chemical transformation of iron chalcogenide superconductors and the insight this gives to the importance of structural features and electron count in determining the existence or not of superconductivity in these compounds. In particular the focus will be on intercalation reactions of iron selenide [1,2], and the value of post-synthetic soft chemical transformations in iron hydroxide selenides Li0.8Fe1.2-ySe(OH) to turn on superconductivity by ensuring defect-free iron selenide layers and reduction of iron below the formal oxidation state of +2 [3]. The work on the iron arsenide and chalcogenide superconductors has driven an expansion of the chemistry of related multi-anion materials including oxide chalcogenides and oxide pnictides. In these cases the use of low temperature transformations to produce new kinetically stable products and tune physical properties have proved to be fruitful, and cases including the control of the structure and magnetism in layered oxide chalcogenides such as Sr2MnO2Cu1.5S2 and its relatives through cation and anion redox processes carried out at low temperatures will be described [4-6].
Références bibliographiques :
[1] Burrard-Lucas M., Free D., Sedlmaier S. et al., « Enhancement of the superconducting transition temperature of FeSe by intercalation of a molecular spacer layer », Nature Materials, vol. 12, 2013, p. 15-19, https://doi.org/10.1038/nmat3464.
[2] Sedlmaier S.J., Cassidy S.J., Morris R.G., Drakopoulos M., Reinhard C., Moorhouse S.J., O’Hare D., Manuel P., Khalyavin D. et Clarke S.J., « Ammonia-rich high-temperature superconducting intercalates of iron selenide revealed through time-resolved in situ X-ray and neutron diffraction », J. Am. Chem. Soc., vol. 136, 2014, p. 630, https://doi.org/10.1021/ja411624q.
[3] Sun H. et al., « Soft Chemical Control of Superconductivity in Lithium Iron Selenide Hydroxides Li1–xFex(OH)Fe1–ySe », Inorg. Chem., vol. 54, no 4, 2015, p. 1958-1964, https://doi.org/10.1021/ic5028702.
[4] Blandy J.N. et al., « Soft chemical control of the crystal and magnetic structure of a layered mixed valent manganite oxide sulfide », APL Mat., vol. 3, 2015, 041520, https://doi.org/10.1063/1.4918973.
[5] Cassidy S.J. et al., « Layered CeSO and LiCeSO oxide chalcogenides obtained via topotactic oxidative and reductive transformations », Inorg. Chem., vol. 58, no 6, 2019, p. 3838-3850, https://doi.org/10.1021/acs.inorgchem.8b03485.
[6] Dey S. et al., « Structural evolution of layered manganese oxysulfides during reversible electrochemical lithium insertion and copper extrusion », Chem. Mater., vol. 33, no 11, 2021, p 3989-4005, https://doi.org/10.1021/acs.chemmater.1c00375.
