A Mossbauer spectral Study of 121 Sb in several oxides

Typical applications for antimony trioxide (Sb2O3) are as flame retardant synergist, as anode material for Li-ion batteries, as catalyst, as glass agent and as major component for several kinds of glasses. Recently, a structural study of the novel Co3Sb4O6F6 compound has been reported [1]. The presence of lone-pair of Sb3+ results in asymmetric coordination and makes this new compound promising like other non-centrosymmetric materials for chemical/biological sensors [1].
Application of 121Sb Mössbauer spectroscopy has been reported frequently [2-4]. We examine the environments of 121Sb in several compounds like α-, β-Sb2O3 and Co3Sb4O6F6 using Mössbauer spectroscopy. Moreover, nuclear forward scattering (NFS) of α- and β-Sb2O3 is compared with conventional Mössbauer spectroscopy. In all these compounds, each Sb is connected to three O in a trigonal bipyramidal geometry. α and β-Sb2O3 have molecular and chain structures, respectively. α-Sb2O3 is built of discrete units composed of four SbO3E, where E corresponds to an electron lone pair. The crystal structure of Co3Sb4O6F6 is made up of a [CoO2F4] network, the voids of the network is filled with Sb4O6. Mössbauer spectra reveal an isomer shifts of ~ -3 mm/s (relative to lnSb) in very good agreement with reported values of -2.7 and -2.8 mm/s of α- and β-Sb2O3 [4], respectively. In addition, a pronounced quadrupole splitting of ~9 mm/s is obtained for these compounds due to the existence of a lone pair of electrons which cause asymmetric charge distribution around the Sb atoms. Remerciements
The European Synchrotron Radiation Facility (ESRF - Grenoble, France) is acknowledged for provision of beamtime at ID-18.