Topotactic synthesis, structure and magnetic properties of a new hexagonal polytype of silver cobaltate(III) AgCoO2+δ

Hervé Muguerra (1) , Claire Colin (2) , Michel Anne (2) , M. -H. Julien (3) , Pierre Strobel (2)

1 NEEL - MagSup - Magnétisme et Supraconductivité
2 NEEL - MRS - Matériaux, Rayonnements, Structure
3 LSP - Laboratoire de Spectrométrie Physique

A new form of delafossite-type AgCoO2+δ was prepared using ion exchange from Na0.75CoO2 in molten AgNO3-NH4NO3 at 175°C. Its structure was determined by Rietveld refinement from XRD data; it is hexagonal, space group P63/mmc, a = 2.871 and c = 12.222 Å. Its structure differs from previously reported AgCoO2 (R-3m, 3R polytype) by the stacking of Co-O layers; in the new phase the 2H stacking of the precursor Na0.75CoO2, consistent with a topotactic ion exchange of Na by Ag. The new phase is found to contain a slight oxygen excess (δ = 0.06). Magnetic susceptibility measurements show the absence of magnetic transition and a weak Curie term, consistent with the non-magnetic character of Co3+ ions.

Mots clés: layered oxide; delafossite structure; topotactic synthesis

Domaines: Science des matériaux [cond-mat.mtrl-sci]; Chimie inorganique; Cristallographie; Supraconductivité [cond-mat.supr-con]

Hervé Muguerra, Claire Colin, Michel Anne, M. -H. Julien, Pierre Strobel. Topotactic synthesis, structure and magnetic properties of a new hexagonal polytype of silver cobaltate(III) AgCoO2+δ. Journal of Solid State Chemistry, 2008, 181, pp.2883. ⟨10.1016/j.jssc.2008.07.031⟩. ⟨hal-00347206⟩