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Layered CeSO and LiCeSo oxide chalcogenides obtained via topotactic oxidative and reductive transformations

DOI: 10.1021/acs.inorgchem.8b03485 DOI Help

Authors: Simon J. Cassidy (University of Oxford) , Michael J. Pitcher (University of Oxford) , Jared J. K. Lim (University of Oxford) , Joke Hadermann (University of Antwerp) , Jeremy P. Allen (Trinity College Dublin) , Graeme W. Watson (Trinity College Dublin) , Sylvia Britto (University of Cambridge) , Elena J. Chong (University of Oxford) , David G. Free (University of Oxford) , Clare P. Grey (University of Cambridge) , Simon J. Clarke (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Inorganic Chemistry , VOL 58 , PAGES 3838–3850

State: Published (Approved)
Published: February 2019
Diamond Proposal Number(s): 13284 , 18786

Open Access Open Access

Abstract: The chemical accessibility of the CeIV oxidation state enables redox chemistry to be performed on the naturally coinage-metal-deficient phases CeM1–xSO (M = Cu, Ag). A metastable black compound with the PbFCl structure type (space group P4/nmm: a = 3.8396(1) Å, c = 6.607(4) Å, V = 97.40(6) Å3) and a composition approaching CeSO is obtained by deintercalation of Ag from CeAg0.8SO. High-resolution transmission electron microscopy reveals the presence of large defect-free regions in CeSO, but stacking faults are also evident which can be incorporated into a quantitative model to account for the severe peak anisotropy evident in all the high-resolution X-ray and neutron diffractograms of bulk CeSO samples; these suggest that a few percent of residual Ag remains. A straw-colored compound with the filled PbFCl (i.e., ZrSiCuAs- or HfCuSi2-type) structure (space group P4/nmm: a = 3.98171(1) Å, c = 8.70913(5) Å, V = 138.075(1) Å3) and a composition close to LiCeSO, but with small amounts of residual Ag, is obtained by direct reductive lithiation of CeAg0.8SO or by insertion of Li into CeSO using chemical or electrochemical means. Computation of the band structure of pure, stoichiometric CeSO predicts it to be a Ce4+ compound with the 4f-states lying approximately 1 eV above the sulfide-dominated valence band maximum. Accordingly, the effective magnetic moment per Ce ion measured in the CeSO samples is much reduced from the value found for the Ce3+-containing LiCeSO, and the residual paramagnetism corresponds to the Ce3+ ions remaining due to the presence of residual Ag, which presumably reflects the difficulty of stabilizing Ce4+ in the presence of sulfide (S2–). Comparison of the behavior of CeCu0.8SO with that of CeAg0.8SO reveals much slower reaction kinetics associated with the Cu1–xS layers, and this enables intermediate CeCu1–xLixSO phases to be isolated.

Subject Areas: Chemistry, Materials


Instruments: I11-High Resolution Powder Diffraction

Other Facilities: ESRF; ISIS

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