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arXiv · 2609.06738

Revealing the origin of ionic conduction in silver-iodide-doped silver phosphate glass

Jennifer Freedberg·Joseph Maduzia·Andias Santoso·Ranveer Singh·Placid Ferreira·Fahad Mahmood
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Abstract

Fast ionic transport is a defining feature of many solid electrolytes, yet its microscopic origin is not fully understood. In the absence of microscopic insights, the development of next-generation solid-state batteries remains largely empirical. Most existing measurements access either the low-frequency transport response or the high-frequency bound polarization, yet the intermediate mesoscopic frequency regime is where ionic transport emerges. By varying the $\mathrm{AgI}$ concentration ($x$) and performing time-domain terahertz spectroscopy (TDTS) in a prototypical glassy electrolyte $\left(\mathrm{AgI}\right)_{x}\left(\mathrm{AgPO_3}\right)_{(1-x)}$, we reveal this intermediate frequency regime and identify a crossover from bound-current-dominated conduction to conductivity arising from short-range dispersive ionic transport. We find that bound polarization associated with the bond-bending motion of the $\mathrm{P{-}O^- -Ag^+}$ motif is present across compositions but is insufficient to produce ionic transport on its own. Transport emerges only when this polarization is embedded in a sufficiently soft $\mathrm{AgPO_3}$ glassy matrix and accompanied by a high carrier density. These ingredients together take the system from a vibrationally bound response to short-range dispersive motion.

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Jennifer Freedberg, Joseph Maduzia, Andias Santoso, Ranveer Singh, Placid Ferreira, Fahad Mahmood. 2026-09-06. Revealing the origin of ionic conduction in silver-iodide-doped silver phosphate glass. https://arxiv.org/abs/2609.06738

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