Ionic-to-Electronic Conductivity Crossover in CdTe-AgI-As₂Te₃ Glasses: An ^110mAg Tracer Diffusion Study

Conductivity isotherms of (CdTe) _x(AgI)_{0.5- x/2}(As₂Te₃)_{0.5- x/2} glasses (0.0 ≤ x ≤ 0.15) reveal a nonmonotonic behavior with increasing CdTe content reminiscent of mixed cation effect in oxide and chalcogenide glasses. Nevertheless, the apparent similarity appears to be partly incorrect. Using ^110mAg tracer diffusion measurements, we show that semiconducting CdTe additions produce a dual effect: (i) decreasing the Ag⁺ ion transport by a factor of ≈200 with a simultaneous increase of the diffusion activation energy and (ii) increasing the electronic conductivity by 1.5 orders of magnitude. Consequently, the conductivity minimum at x = 0.05 reflects an ionic-to-electronic transport crossover; the silver-ion transport number decreases by 3 orders of magnitude with increasing x.