Structural investigation into the non-Arrhenius behavior of fast ion conducting sulfide glasses.

摘要

The glass forming range of the Ag₂S + B ₂S₃ + GeS₂ ternary system was investigated and a wide range of ternary glasses were obtained. The thermal properties of these thioborogermanate glasses were studied by DSC and TMA. The Raman, IR and NMR spectroscopy were used to explore the short-range order structure of the binary (Ag-B) and (Ag-Ge) and ternary (Ag-B-Ge) glasses. The Raman and NMR studies show that Ag₂S goes into the GeS₂ subnetwork to form pyrothiogermanate groups before going to the B₂S₃ subnetwork. In doing so, it is suggested that [B₁₀S₁₈6− ] superstructure exist in Ag₂S + B₂S₃ and Ag₂S + B₂S₃ + GeS₂ glasses. From these observations, a structural model for these glasses has been developed and proposed.; Fast Ion Conducting (FIC) glasses of composition xAg₂S + (1−x)[0.5B ₂S₃ + 0.5GeS₂] have been studied using neutron scattering to investigate their short-range order structure and intermediate range order structure. The total correlation functions T(r) were fitted with Gaussian functions and the bond length and coordination numbers of Ge-S, Ag-S and Ag-Ag correlations are determined. It is found that the Ag₂S + B₂S₃ + GeS₂ glasses are composed of a B ₂S₃ network containing [B₁₀S₁₈ 6−] superstructure and an over-doped GeS_4/2 network. The existence of boron superstructure contributes to the high mobility and conductivity of Ag ions. The temperature and composition dependence of Ag-Ag correlation supports that Ag ion interaction is a factor that cannot be ignored at relatively high temperature and could explain the origin of the non-Arrhenius behavior.; Conductivity measurements of zAgI + (1−z)[xAg₂S + (1−x)(0.67B ₂S₃ + 0.33GeS₂)] fast ion conducting glasses were performed to explore the non-Arrhenius behavior above room temperature. A distinct non-Arrhenius deviation is observed that causes the dc conductivity to be lower than the expected values. Ion Trapping Model has been used to describe the non-Arrhenius conductivity and fit the experimental data. It is found that the model is able to accurately reproduce the non-Arrhenius temperature dependence of the conductivity of these optimized fast ion conducting glasses. The model has only one independently adjustable parameter and it provides a physical picture of the cause of non-Arrhenius deviation.