Effect of halide ions on Li⁺ ionic conductivity in oxyhalo-borate glasses

The electrical conductivity has been measured for the glasses in the system B₂O₃–Li₂O–Li₂X₂(X = F, Cl, Br), where Li₂O is replaced by Li₂X₂ with Li content kept constant. The conductivity decreases for F glasses and increases for Cl and Br glasses with increasing halide ion content, which is caused by the increase in the activation energy for F glasses and the decrease for Cl and Br glasses. The analysis of the activation energy in terms of the Anderson-Stuart model indicates that, with the increase in LiX, Δ E_b, (the electrostatic energy) increases for F glass, whereas ΔE_s (the strain energy) and ΔE_b decrease for Cl or Br glasses. The effects of F⁻ and other halide ions are attributed to a stronger interaction between Li and F, and to expanded and weakened glass network due to accommodation of Br⁻ and Cl⁻ ions.