Publication: Sodium-Poor, Hydroxyl-Rich, Defective Na<inf>2</inf>Ti<inf>3</inf>O<inf>7</inf> Prepared by γ-Irradiation and Its Enhanced Proton Conductivity
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Issued Date
2024-09-30
Resource Type
ISSN
00201669
eISSN
1520510X
Scopus ID
2-s2.0-85205403228
Pubmed ID
39291623
Journal Title
Inorganic Chemistry
Volume
63
Issue
39
Start Page
18073
End Page
18082
Rights Holder(s)
SCOPUS
Bibliographic Citation
Inorganic Chemistry Vol.63 No.39 (2024) , 18073-18082
Suggested Citation
Maluangnont T., Sangtawesin T., Pulphol P., Khamman O., Reunchan P., Gotoh K., Vittayakorn N. Sodium-Poor, Hydroxyl-Rich, Defective Na<inf>2</inf>Ti<inf>3</inf>O<inf>7</inf> Prepared by γ-Irradiation and Its Enhanced Proton Conductivity. Inorganic Chemistry Vol.63 No.39 (2024) , 18073-18082. 18082. doi:10.1021/acs.inorgchem.4c02768 Retrieved from: https://hdl.handle.net/20.500.14740/20697
Corresponding Author(s)
Other Contributor(s)
Abstract
The use of γ-irradiation to tailor the physicochemical properties of materials is not widely applied to layered alkali metal oxides. Herein, we show that γ-irradiation (up to 400 kGy) of Na2Ti3O7 leads to a sodium-poor, hydroxyl-rich analogue where the layered structure, plate-like morphology, and textural properties are preserved. The deintercalation of sodium ions modifies the Ti-O bond lengths and expands the unit cell; the latter is supported by density functional theory (DFT) calculations. 23Na solid-state NMR suggests the transport of the symmetric, 7-fold Na2 sites to an intermediate environment, which is closer to the asymmetric, 9-fold Na1 sites. An 8 wt % mass loss (1.4 mol water/mol titanate) is observed, indicating an increased concentration of protons/hydroxyls. These hydroxyl groups (i.e., lattice protons) possess higher thermal stability than solely surface-adsorbed ones in the nonirradiated sample. At 200-400 kGy, the proton conduction (50 °C and ∼70% RH) of ∼10-6 S·cm-1 is 1 order of magnitude larger than that in the nonirradiated sample; the relaxation time decreases from 30 to 2-6 μs with γ-irradiation. The γ-dose dependence of dielectric loss is also present and analyzed using the Jonscher universal power law, indicating the low-frequency dispersion behavior characteristics of high charge densities.