Fluorine Conducting Ceramics Based on BiF₃

The temperature dependence of the ionic conductivity of a Bi_0.94Ba_0.06F_2.94 solid electrolyte ceramic sample has been studied by impedance spectroscopy in the temperature range of 293–473 K. The ceramics obtained by the solid-state synthesis (873 K, 3 h) in a closed Cu ampoule is a heterovalent solid solution of tysonite structure (sp. gr. \(P\bar {3}c1\) ) with the lattice parameters a = 7.1482(8) Å and c = 7.3279(5) Å. The room-temperature conductivity and its activation enthalpy are, respectively, σ_cer = 3 × 10⁻⁵ S/cm and ΔH_σ = 0.49 ± 0.05 eV. The ion-conducting properties of the isostructural Bi \(_{{1 - y}}\) Ba_yF \(_{{3 - y}}\) and La \(_{{1 - y}}\) Ba_yF \(_{{3 - y}}\) solid electrolytes with similar ionic radii of the matrix cations (1.17 and 1.16 Å for Bi³⁺ and La³⁺, respectively) have been compared. The conductivity of Bi_0.94Ba_0.06F_2.94 ceramics at 473 K exceeds the electrical conductivity of La_0.95Ba_0.05F_2.95 ceramics and single crystal by factors of 6 and 3.3, respectively.