Fluorine conducting ceramics based on BiF3

The temperature dependence of the ionic conductivity of a ceramic sample of the Bi0.94Ba0.06F2.94 solid electrolyte was studied using impedance spectroscopy in the temperature range 293–473 K. The ceramics was obtained by solid-phase synthesis (873 K, 3 h) in a closed Cu ampoule and is a heterovalent solid solution of tysonite structure (space group) with lattice parameters a = 7.1482(8) and c = 7.3279(5) Å. The conductivity value at room temperature and its activation enthalpy are equal to σcer = 3 × 10–5 S/cm and DHs = 0.49 ± 0.05 eV, respectively. The ion-conducting properties of isostructural solid electrolytes Bi1–yBayF3–y and La1–yBayF3–y with similar values of ionic radii of matrix cations (1.17 and 1.16 Å for Bi3+ and La3+, respectively) are compared. The conductivity at 473 K of Bi0.94Ba0.06F2.94 ceramics exceeds the electrical conductivity of ceramics and La0.95Ba0.05F2.95 single crystals by 6 and 3.3 times, respectively.