Interactions magnetiques hyperfines et quadrupolaires combinees pour les ions d'impuretes 119Sn2+ dans Cr2O3

Mössbauer study of the Impact of Hydrogen Fluoride on Tin Probe Ions Located on the Surface of Cr2O3 microcrystals

“…The "nal treatment is performed under H #ow at 1200 K for 10 h in a quartz reactor equipped with a lateral thin-window sample cell for in situ MoK ssbauer measurements. At the end of this annealing the tin ions are reduced to the #II state and located at the interface +Cr O crystallites/H , (1,7). This surface location is in particular re#ected by the high sensitivity of the Sn(II) ions to air exposure which results in their instantaneous reoxidation to the #IV state.…”

“…This surface location is in particular re#ected by the high sensitivity of the Sn(II) ions to air exposure which results in their instantaneous reoxidation to the #IV state. The daughter Sn(IV) species remain surface-located as shown by XPS measurements: the Sn/Cr ratio derived from XPS data is found to be 40 times greater than the overall ratio, and Ar> ion bombardment rapidly removes an appreciable part of the tin ions (1).…”

“…The starting material, Sn(II)/Cr O , to be exposed to HF was obtained according to the method described in (1). The initial stage of this process involves coprecipitation of Cr(III) and Sn(IV) ions in the form of X-ray amorphous hydroxide (atomic ratio Sn:Cr"0.003; 92% enrichment of the dopant in Sn MoK ssbauer isotope).…”

“…E!ectively, in this case, the MoK ssbauer spectra of the probe provide information concerning not only its anionic neighborhood (through isomer shift and quadrupole splitting values) but also its cationic environment thanks to the magnetic e!ects observed. This possibility has already been illustrated in the case of chromium sesquioxide (1), which can be surface-doped with Sn(II) (the corresponding product is referred to as Sn(II)/Cr O ). Cr O is antiferromagnetic and, below its NeH el temperature (¹ , "308 K (2)), the magnetic moments of the Cr(III) cations produce spin polarization of the electron shell of the neighboring tin ions, which results in Zeeman splitting of the Sn MoK ssbauer spectra.…”

Mössbauer Study of the Chemical Behavior of Tin Dopant Atoms on the Surface of Cr2O3Microcrystals: Transformations Induced by Exposure to Ambient Atmosphere after Contact with H2S

“…Les e´chantillons destine´s a`eˆtre expose´s a`l'air ont e´teś ynthe´tise´s selon une me´thode de´ja`utilise´e (3,7,9). Dans un premier temps, un oxyde hydrate´amorphe de Cr (III) contenant le dopant Sn (IV) (enrichi a`92% en Sn) avec le rapport atomique Sn/Cr"0,003 est obtenu par copre´cipi-tation.…”