Crystal Structure and Ionic Conductivity of Cesium Trifluoromethyl Sulfonate, CsSO 3 CF 3

The crystal structures of the room and the high temperature modifications of cesium trifluoromethyl sulfonate were solved from high resolution X‐ray powder diffraction data. At room temperature, α‐CsSO 3 CF 3 crystallizes in the monoclinic space group P 2 1 with lattice parameters a = 9.7406(2) Å, b = 6.1640(1) Å, c = 5.4798(1) Å, and β = 104.998(1)°; Z = 2. At temperatures above T = 380 K, a second order phase transformation towards a disordered C‐centered orthorhombic phase in space group Cmcm occurs with lattice parameters at T = 492 K of a = 5.5074(3) Å, b = 19.4346(14) Å, and c = 6.2978(4) Å; Z = 4. Within the crystal structures, the triflate anions are arranged in double layers with the apolar CF 3 ‐groups pointing towards each other. The cesium ions are located between the SO 3 ‐groups. CsSO 3 CF 3 shows a specific ion conductivity ranging from σ = 1.06·10 −8 Scm −1 at T = 393 K to σ = 5.18·10 −4 Scm −1 at T = 519 K.