Ion conductivity of the plastic phase of the organic salt [(C4H9)4N]BF4

Based on the thermal and X-ray diffraction analysis, NMR spectroscopy, and ion conductivity data it was shown that the organic salt [n-Bu4N]BF4 has an orientationally disordered phase with a primitive cubic unit cell (space group \(P\bar 43n\); unit cell parameter ac = 1.4886(2) nm) in the temperature range 62–161°C. The mobility of molecular fragments and anions increased during the phase transition, and the ion conductivity was relatively high, reaching ∼10−6 S/cm at 150°C.