The impedance of the hydrogen fluorides was investigated as a function of temperature, and in the presence of HF and H2O. A comparison of results for various electrode materials (graphite, Ag, Pd, Sn|SnF2, and Sn|SnF2|LaF3) was used to clarify the contributions made by fluoride ions and protons to the net charge transport. All 3 of the materials exhibited a marked, and almost reversible, increase in conductivity in the presence of gases that acted as proton donors. For BaHF3, the results revealed the mobility of fluoride ions (E = 0.54eV) as well as the net mobility of protons. The latter was explained in terms of proton exchange due to internal acid–base reactions of the protonated anions. At ambient temperatures, KHF2 became conducting only when exposed to HF or H2O. The NH4HF2 already exhibited a higher conductivity than that of BaHF3 in a dry atmosphere; increasing less with humidity than for the other 2 materials. This indicated the existence of an intrinsic proton mobility in NH4HF2.

Ion Transport in Alkaline and Earth Alkaline Hydrogen Fluorides. C.Kröger, H.Niggemeier, H.D.Wiemhöfer, O.Glumov, I.Murin: Solid State Ionics, 2002, 154-155, 487-95