Preparation of proton conducting ionic glasses in the systems CsHSO4–MHSO4 (M = Na, K, Rb)

Glass formation in the systems CsHSO4–MHSO4 (M = Na, K, and Rb) was examined by the melt quenching technique using a twin roller, and thermal and ionic conducting properties of the glasses were investigated. To avoid the dehydration reaction, the melts were quenched immediately after the confirmation of complete melting. In the CsHSO4–NaHSO4 system, glasses were obtained at the composition of x = 50, 60 and 70 in xCsHSO4 (100 − x)NaHSO4 (mol%). However, vitrification was not observed in the CsHSO4–KHSO4 and CsHSO4–RbHSO4 systems. The FT–IR spectra of the glasses obtained by the quenching of molten CsHSO4 and NaHSO4 showed that these glasses consist of isolated HSO4− units, and the glasses were confirmed to be “ionic glass” which consist of only isolated ionic species. From the DSC measurements, the 70CsHSO4·30NaHSO4 ionic glass was found to have the glass transition temperature of 17 °C, and crystallization temperature of 58 °C. The ionic conductivity of the 70CsHSO4 · 30NaHSO4 glass is in the order of 10− 5 S cm− 1 at room temperature, which is higher than that of CsHSO4 low-temperature phase. After heating above the crystallization temperature, the ionic conductivity rapidly decreased. These results suggest that vitrified solid acids have advantages in proton conduction compared with the low-temperature phase of solid acids.