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The opposing effect of gamma irradiation on proton and sodium ion conduction in Na2Ti3O7 and its defective analog
Author(s)
Date Issued
October 1, 2026
Type
Article
Abstract
It is known that γ-irradiation of Na2Ti3O7 induces Na + ion deintercalation, oxygen-vacancy formation, and proton/water incorporation, yielding the defective phase Na2- x H0.5 x Ti3O7-0.5 x (OH)0.5 x with multiple charge carriers. Although Na2Ti3O7 is a well-studied ion conductor, charge-transport details in its γ-irradiated analogs remain limited. Here, we report their AC conductivity and dielectric properties under a temperature cycle (RT→350 °C→RT). Proton conduction dominates at ambient temperature but diminishes upon heating. This produces a dehydration-driven increase of resistivity known as the apparent Positive Temperature Coefficient of Resistivity (PTCR) effect, consistent with the Heywang model recently applied to water-adsorbing ceramics. Proton conductivity increases with γ-irradiation dose up to 200 kGy, then decreases at 400 kGy due to excessive structural disorder. At high temperatures, Na+ ion conduction prevails and follows Arrhenius behavior, with activation energy decreasing with dose. This discrepancy might be understood considering that Na+ ion conduction is governed primarily by its concentration rather than mobility; excessive doses lower activation energy but deplete Na+ ions and decrease conductivity. Dielectric-loss fitting using Jonscher's universal dielectric response (UDR) indicates that proton-transport pathways are sensitive to thermal history, whereas Na+ ion conduction exhibits low-frequency dispersion (LFD) across all conditions.
Citation
Radiation Physics and Chemistry, 247, 2026