Structural characterization of silver thioborosilicate glasses

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Fast ion conducting glasses of composition zAgI+(1− z)[0.525Ag 2S+0.475(0.5B 2S 3+0.5SiS 2]), where 0.0⩽ z⩽0.4, have been studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry, and nuclear magnetic resonance (NMR), Raman, and infrared (IR) spectroscopies to investigate their short-range order (SRO) structure. These glasses are of significant interest due to the observation that they exhibit significant non-Arrhenius behavior in their ionic conductivity. A thorough study of the SRO of these glasses is being conducted to determine if there is an underlying structural origin to the non-Arrhenius behavior of the conductivity. The NMR, Raman and IR spectra show that these glasses are comprised primarily of silicon sulfide (Ag 2Si(S 2)S 2/2 and boron sulfide (AgBS 4/2) tetrahedra with small amounts of B 3S 6 thioboroxyl six-membered rings and BS 3/2 trigonal units in the glassy matrix. The addition of AgI appears dissolve into glass interstitially without significant modification of the SRO of the glasses. SEM experiments show the samples are homogeneous with little oxide contamination and the XRD experiments show that the samples are glassy with little evidence of crystallization. As with other AgI-doped glasses, the AgI systematically decreases the glass transition temperature. So far, there is no evidence of significant structural uniqueness at the SRO level to these glasses that would suggest a cause for the non-Arrhenius temperature dependence of the conductivity. More detailed neutron scattering and NMR studies of these glasses are in progress and will be used to determine if the structural origin of this behavior can be found at longer length scales.