Cation site preferences in layered oxide chalcogenides, synthesis, structures and magnetic ordering in Sr3-xCaxFe2O5Cu2Ch2 (Ch = S, Se; x = 1, 2)

Journal article

Solid solutions between the known compounds Ca2FeO3CuCh and Sr2FeO3CuCh (Ch = S, Se) in which there are two fairly similar sites (8 and 9 coordinate) for the alkaline earth cations are not attainable under standard high temperature solid state syntheses under thermodynamic control. Instead compounds with greater condensation of FeO5 square pyramids form as these afford one 8-coordinate site and one 12-coordinate site for the alkaline earths which is better suited to the sizemismatched cations in the compounds Sr3-xCaxFe2O5Cu2Ch2 (Ch = S, Se; x = 1, 2). Sr2CaFe2O5Cu2S2, SrCa2Fe2O5Cu2S2, Sr2CaFe2O5Cu2Se2 and SrCa2Fe2O5Cu2Se2 all crystallise in the tetragonal space group I4/mmm with two formula units in the unit cell with the crystal structure first described for Sr3Fe2O5Cu2S2. Oxide slabs composed of vertex-sharing FeO5 square pyramids are separated by Cu2Ch2 anti-fluorite-type layers. The larger Sr2+ ions have a strong preference for the 12-coordinate site in the oxide slabs, while Ca2+ cations dominate the 8-coordinate sites separating the oxide and chalcogenide slabs. Powder neutron diffraction reveals that all the compounds display antiferromagnetic long range ordering of the Fe3+ moments with ordering temperatures well above room temperature and exceeding 526 K in the case of Ca2SrFe2O5Cu2Se2.

Authors: Sheath, BC; Cassidy, SJ; Clarke, SJ

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Elsevier
• Journal: Journal of Solid State Chemistry
• Volume: 293
• Issue: January 2021
• Article number: 121761
• Publication date: 2020-10-08
• Acceptance date: 2020-09-27
• DOI: 10.1016/j.jssc.2020.121761
• ISSN: 0022-4596
• Language: English
• Keywords: FFR