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

Area of Science:

• Materials Science
• Solid State Chemistry
• Condensed Matter Physics

Background:

• Chalcogenide glasses exhibit complex conductivity behaviors.
• Mixed cation effects are observed in various glass systems.
• Understanding transport mechanisms in these materials is crucial for applications.

Purpose of the Study:

• To investigate the effect of cadmium telluride (CdTe) on the conductivity of (AgI)x(As2Te3)y glasses.
• To elucidate the underlying transport mechanisms, distinguishing between ionic and electronic contributions.
• To explore the phenomenon of ionic-to-electronic transport crossover.

Main Methods:

• Synthesis and characterization of (CdTe)x(AgI)0.5-x/2(As2Te3)0.5-x/2 glasses with varying CdTe content (0.0 ≤ x ≤ 0.15).
• Measurement of conductivity isotherms to observe conductivity changes with composition.
• 110mAg tracer diffusion experiments to quantify silver ion (Ag+) mobility.
• Determination of ionic and electronic conductivity contributions.

Main Results:

• Conductivity isotherms showed nonmonotonic behavior with increasing CdTe content.
• Silver ion (Ag+) transport decreased significantly (≈200 times) with increasing CdTe.
• Electronic conductivity increased by 1.5 orders of magnitude with increasing CdTe.
• A conductivity minimum at x = 0.05 indicated a crossover from ionic to electronic transport.
• Silver-ion transport number decreased by three orders of magnitude as CdTe content increased.

Conclusions:

• Semiconducting CdTe additions induce a dual effect on glass conductivity: suppressing Ag+ ion transport while enhancing electronic conductivity.
• The observed conductivity minimum is a direct consequence of an ionic-to-electronic transport crossover.
• The study provides critical insights into the charge transport mechanisms in these complex chalcogenide glass systems.