Effect of homovalent (I−Br−) ion substitution on the ionic conductivity of LiI1−x Brx systems
Abstract The study of electric conductivity in the whole range of compositions of mixed LiI 1− x Br x crystals has shown that doping of pure lithium halide (LiI or LiBr) by homovalent substitution leads to an increase in conductivity. This enhancement is essentially pronounced in the solid solution domains near the compositions of pure compounds (x 0.90). Maximum conductivity is attained for the two phase composition LiI 0.75 Br 0.25 (5 × 10 −7 S cm −1 at 293 K) compared to those of starting compounds (4 × 10 −8 : LiI and 9 × 10 −9 : LiBr at 293 K). An Arrhenius behaviour of the conductivity evolution versus the inverse of the temperature shows that variations in conductivity are related to those of the activation energy whose minimum is close to 8.7 Kcal mole −1 . Lattice strain involved by substituting anions of different raddi could be the factor which increase the defect population.