use of Mossbauer Spectroscopy for the Characterization of Order/Disorder Phenomena in Tin Containing Ionic Conductors and for Making Predictions Regarding Possible Electron COntribution to the Conduction

摘要

Mossbauer spectroscopy has been seldom used for the characterization of ionic concuctors. However, since the introdcution of divalent tin in MF_2 fluorties to form MSnF_4, PbSn_4F_10 or the Pb_(1-x)Sn_xF_2 solid solution, all of which have structures closely related to the fluorite type, results in an enhancement of the fluoride ion coductivity by up to three orders of magnitued, and since 119Sn is the second best Mossbauer nuclide, it seems that the Mossbauer technique could provide useful inofrmation about how tin(II) mofifies the fluorite structure and leads to such a tremendous enhancement of the fluoride ion mobility. The MF_2/SnF_2 systems contain some number of materials that show order/disorder phenomena which make it difficult to understand them from diffraction data only. Mossbauer spectroscopy has been invaluable in helping understand the local structure at tin. By probing hte valence electronic structure of tin, we can also make predictios on the possible long range mobility of the tin(II) non-bonded elelctron pair, which would make the material an electronic conductor or a mixed conductor.