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Topochemical Fluorination of n = 2 Ruddlesden–Popper Type Sr3Ti2O7 to Sr3Ti2O5F4 and Its Reductive Defluorination

Wissel, Kerstin and Vogel, Tobias and Dasgupta, Supratik and Fortes, Andrew Dominic and Slater, Peter R. and Clemens, Oliver (2020):
Topochemical Fluorination of n = 2 Ruddlesden–Popper Type Sr3Ti2O7 to Sr3Ti2O5F4 and Its Reductive Defluorination.
In: Inorganic Chemistry, 59 (2), pp. 1153-1163. American Chemical Society, ISSN 0020-1669,
DOI: 10.1021/acs.inorgchem.9b02783,
[Article]

Abstract

Within this study, we show that a sequence of substitutive topochemical fluorination of the n = 2 Ruddlesden-Popper type compounds Sr3Ti2O7 to Sr3Ti2O5F4 followed by reductive topochemical defluorination reactions between the oxyfluoride and the reducing agent sodium hydride allows for a substantial reduction of the oxidation state of Ti due to selective extraction and hydride substitution of fluoride ions. The oxyfluoride Sr3Ti2O5F4 has been synthesized and characterized structurally for the first time. The defluorination experiments have been conducted at temperatures as low as 300 degrees C, enabling also the reduction of this metastable compound. The evolution of phase fractions and unit cell volumes of various reduced phases as well as of side products has been monitored by an X-ray diffraction study as a function of the amount of sodium hydride used. Strong structural changes within the reduced phases, involving considerable decreases in the c lattice parameters partly accompanied by symmetry, lowering have been observed. To gain a deeper understanding of the structural changes, selected reduction reaction products have been further investigated by coupled analysis of X-ray and neutron powder diffraction data. Moreover, changes in the oxidation state of Ti have been studied using magnetic measurements and Xray photoelectron spectroscopy examining differences between the bulk and the surface properties. Additionally, similarities and differences between previously published results on the topochemical defluorination of the n = 1 Ruddlesden-Popper type compound Sr2TiO3F2 are discussed.

Item Type: Article
Erschienen: 2020
Creators: Wissel, Kerstin and Vogel, Tobias and Dasgupta, Supratik and Fortes, Andrew Dominic and Slater, Peter R. and Clemens, Oliver
Title: Topochemical Fluorination of n = 2 Ruddlesden–Popper Type Sr3Ti2O7 to Sr3Ti2O5F4 and Its Reductive Defluorination
Language: English
Abstract:

Within this study, we show that a sequence of substitutive topochemical fluorination of the n = 2 Ruddlesden-Popper type compounds Sr3Ti2O7 to Sr3Ti2O5F4 followed by reductive topochemical defluorination reactions between the oxyfluoride and the reducing agent sodium hydride allows for a substantial reduction of the oxidation state of Ti due to selective extraction and hydride substitution of fluoride ions. The oxyfluoride Sr3Ti2O5F4 has been synthesized and characterized structurally for the first time. The defluorination experiments have been conducted at temperatures as low as 300 degrees C, enabling also the reduction of this metastable compound. The evolution of phase fractions and unit cell volumes of various reduced phases as well as of side products has been monitored by an X-ray diffraction study as a function of the amount of sodium hydride used. Strong structural changes within the reduced phases, involving considerable decreases in the c lattice parameters partly accompanied by symmetry, lowering have been observed. To gain a deeper understanding of the structural changes, selected reduction reaction products have been further investigated by coupled analysis of X-ray and neutron powder diffraction data. Moreover, changes in the oxidation state of Ti have been studied using magnetic measurements and Xray photoelectron spectroscopy examining differences between the bulk and the surface properties. Additionally, similarities and differences between previously published results on the topochemical defluorination of the n = 1 Ruddlesden-Popper type compound Sr2TiO3F2 are discussed.

Journal or Publication Title: Inorganic Chemistry
Journal volume: 59
Number: 2
Publisher: American Chemical Society
Uncontrolled Keywords: Microwave Dielectric-Properties, Iron-Oxide, Insertion
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Fachgebiet Materialdesign durch Synthese
Date Deposited: 19 Feb 2020 07:27
DOI: 10.1021/acs.inorgchem.9b02783
Official URL: https://doi.org/10.1021/acs.inorgchem.9b02783
Projects: This work was funded by the German Research Foundation within the Emmy Noether program (Grant CL 551/2-1)., Neutron diffraction beamtime on HRPD at ISIS was provided by the Science and Technology Facilities Council (STFC) (1720040).
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