Bernard Ducourant

121Sb Mössbauer spectral and related studies on Sb(III) complexes

The bonding and structural features of antimony(III) complexes of the type, (PriO)SbL and Sb2L3 are described (where L is the dianion of semicarbazone or thiosemicarbazone). The Mossbauer spectra are typical of Sb(III) complexes in which the non-bonding pair of electrons is stereochemically active. The thiosemicarbazone complexes show more negative isomer shifts compared to the semicarbazone complexes.

Complex formation between antimony trifluoride and alkali-metal sulphates: the X-ray crystal structure of K2SO4·SbF3 and antimony-121 Mössbauer studies of some related compounds

The X-ray crystal structure of K2SO4·SbF3 is reported. It crystallizes in the orthorhombic space group P212121, with a= 5.601(2), b= 9.072(4), c= 14.180(6)A, and Z= 4 and a final R= 0.035. The antimony environment is that of a distorted octahedron, SbF3O2E, where E represents the non-bonding electron pair of SbIII The 121Sb Mossbauer data of this and other M2SO4·SbF3 complexes are interpreted in terms of SbX5E and SbX6E environments. In all cases the non-bonding electron pair is stereochemically active.

Structure and enhanced proton conductivity in composites of antimony(III) oxide and mordenite

Abstract Composite proton-conducting materials containing mordenite and micro-particulate hydrous Sb 2 O 3 have been prepared. Materials characterisation employed X-ray powder diffractometry (XRD), 29 Si and 27 Al MAS-NMR, 121 Sb Mossbauer spectroscopy and a.c. conductivity studies. Sb 2 O 3 -mordenite composites show conductivity enhancements (relative to parent Na mordenite) similar to those reported for ‘tin mordenite’; components in both systems comprise a hydrous oxide and de-aluminated zeolite. Both XRD and MAS-NMR reveal de-alumination/disruption of the framework of the zeolite to be less extensive than in previously investigated composites of antimonic acid and mordenite, which did not exhibit conductivity enhancements.

Syntheses, étude structurale par diffraction X, spectroscopies infrarouge et Mössbauer de K2SeO4SbF3 · 12H2O

The X-ray crystal structure of K2SeO4SbF3 · 12H2O is reported. It crystallizes in the orthorhombic space group Pnma with a= 10.560(5), b = 12.803(4), c = 11.806(4)A, Z = 8, and a final R = 0.034. The antimony environment is that of a distorted dodecahedron SbF3O4E where E represents the nonbonding electron pair of SbIII. For K2SeO4SbF3 · 12H2O, infrared and antimony-121 Mossbauer spectra have been recorded; the data of the title compound and of other complexes are interpreted in terms of SbX5E and SbFX6E distorted environments. In all cases the nonbonding electron pair is stereochemically active.

Investigations of structure and protonic conductivity in composites of hydrous antimony(V) oxide and mordenite

Composites prepared by hydrolysis of antimony pentachloride in the presence of the zeolite mordenite have been characterised by X-ray powder diffractometry (XRD), 29Si and 27AL MAS NMR, 121Sb Mossbauer spectroscopy and investigations of ac conductivity as a function of relative humidity (RH). Both XRD and MAS NMR studies show degradation of the zeolite framework, the extent of the damage depending upon the amount of antimony pentachloride used in the preparation. Mossbauer spectra are consistent with the antimony-containing component being amorphous antimonic acid, as anticipated from the preparative conditions. The composites are protonic (H +) conductors, but do not show the enhanced conductivities characteristic of ‘tin mordenites’, which show the same disruption of the zeolite framework.

Structural and physical properties of electrochromic WO3 films prepared by CVD or thermal vaporization

Optical, electrical, and structural properties of electrochromic, amorphous, or polycrystalline WO3 thin films prepared by thermal vaporization or chemical vapor deposition (CVD) have been studied for samples in colored and bleached states. During the electrical coloration process, a shift of the absorption peak toward higher energies and an increase in the conductivity were observed for all samples. In the same time for the polycrystalline samples a structural change from monoclinic to cubic structure appeared and an increase in the reflectivity in the infrared wavelength range. The crystal structure of colored films changed back to the initial state when the films were electrically bleached, however, the optical and electrical properties were not absolutely reversible. It is possible that a fraction of hydrogen cations still remained inside bleached films and did not contribute to the coloration. An x ray diffraction study during the oxidation in air of a colored sample as a function of time indicates the possibility of following the kinetics of the electrochromic process from the shift of the XRD peaks.

Interaction trifluorure d'antimoine-seleniates alcalins: Structure cristalline de K2SeO4(SbF3)2 · H2O

Abstract The systems SbF 3  M 2 SeO 4 ( M = K, Rb, and Cs) in selenic aqueous solution have been studied. Two kinds of compounds have been isolated: molecular addition compounds K 2 SeO 4 (SbF 3 ) 2 , Rb 2 SeO 4 (SbF 3 ) 2 , K 2 SeO 4 (SbF 3 ) 2 · H 2 O, and double decomposition compounds M SbF 2 SeO 4 . The crystal structure of K 2 SeO 4 (SbF 3 ) 2 · H 2 O has been solved from an X-ray single crystal study (orthorhombic P 2 1 2 1 2 1 , R = 0.033 with 1251 reflexions). There are two types of antimony atoms both with monocapped octahedral environment 3.3.1 AX 6 E. The SeO 4 entities weakly linked with four antimony atoms show a tetrahedral geometry slightly distorded. Infrared and Raman spectra of the different phases which have been synthesized show a more important distortion of the SeO 4 group in the M SbF 2 SeO 4 compounds wherein the SbF 2 groups are more strongly linked.

Investigations of structure and protonic conductivity in the so-called tin zeolites

‘Tin zeolites’, composites containing a zeolite and SnO2, have been produced from parent zeolites (mordenite, zeolites X, Y and A) by thermal and microwave methods. Materials characterisation employed X-ray powder diffractometry (XRD), 29Si and 27AL MAS NMR, 119Sn Mossbauer spectroscopy, and ac conductivity investigations. Both XRD and MAS NMR studies show degradation of the zeolite framework in materials prepared by the thermal route. The extent of the damage depends upon the tin salt used in synthesis and is higher for those zeolites with higher Al contents. Mossbauer spectra are dominated by a central peak arising from microdispersed SnO2, but a second SnIV environment is also present in materials prepared thermally from zeolites X, Y and A. All the ‘tin zeolites’ exhibit protonic conductivities greater than those of the parent zeolites, with thermally prepared samples exhibiting conductivities up to an order of magnitude greater than corresponding materials prepared by the microwave method.