Giant humidity dependence of conductivity in a single exfoliated titania nanosheet

Tanaka, Ayaka; Hatakeyama, Kazuto; Oku, Azusa; Matsuzaki, Koji; Saitou, Natsumi; Yokoi, Hiroyuki; Taniguchi, Takaaki; Matsumoto, Yasumichi; Hara, Masahiro

doi:10.1063/1.4872469

Cited by 5 publications

(3 citation statements)

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“…25−27 In these cases, water can be incorporated either as (i) crystalline hydrates at the interlayer space, 28,29 (ii) noncrystalline hydrates at the grain boundary/porosity/ external surfaces, 11,30,31 or (iii) the combination of these two. 7,32 Investigating the effects of noncrystalline water will widen our fundamental understanding of water-induced conductions, complementing extensive works on the crystalline hydrated (i.e., protonic) titanates 1,28,33,34 analogues, 2,35 offering ways to enhance the sensing performances, and so on.…”

Section: ■ Introductionmentioning

confidence: 99%

“…The adsorption of atmospheric water on the surfaces of functional ceramics promotes proton/hydroxide conduction and generates additional charge carriers, leading to applications such as proton batteries, humidity sensors, and so forth. − However, this phenomenon complicates the understanding of the nature of original conducting species in a pristine, water-free material. The literature provides several examples of this oftentimes neglected contribution of surface-adsorbed water to the observed electrical properties.…”

Section: Introductionmentioning

confidence: 99%

“…It is well known that alkali-containing ceramics are prone to atmospheric water adsorption. Among these, several members of the alkali titanate family have received increasing attention thanks to their superionic conduction, giant/colossal dielectric permittivity, ,, and water-induced transport properties. − The alkali titanates show rich structural chemistry and compositional flexibility, as exemplified by the layered or tunnel-structured Andersson–Wadsley-type A 2 O· n TiO 2 (A = alkali; 1 ≤ n ≤ 6) and the lepidocrocite-type layered A x Ti 2– y M y O 4 (M = transition metals of the first row). − In particular, the layered alkali titanates can undergo exfoliation into nanosheets, which are an important component in nanoelectronics or triboelectric nanogenerators. − In these cases, water can be incorporated either as (i) crystalline hydrates at the interlayer space, , (ii) noncrystalline hydrates at the grain boundary/porosity/external surfaces, ,, or (iii) the combination of these two. , Investigating the effects of noncrystalline water will widen our fundamental understanding of water-induced conductions, complementing extensive works on the crystalline hydrated (i.e., protonic) titanates ,,, and the nanosheet analogues, , offering ways to enhance the sensing performances, and so on.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Adsorbed Water and Temperature on the Universal Power Law Behavior of Lepidocrocite-Type Alkali Titanate Ceramics

et al. 2021

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The ubiquitous (re)adsorption of atmospheric water by functional ceramics leads to some applications such as humidity sensing; at the same time, this phenomenon complicates the understanding of the nature of original conducting species. We presented herein the effects of adsorbed water on the electrical properties and charge transport of K0.8Zn0.4Ti1.6O4, Cs0.7Zn0.35Ti1.65O4, and Cs0.6K0.1Zn0.35Ti1.65O4 lepidocrocite-type alkali titanate ceramics. A small amount of atmospheric water (0.02–0.33 mol/mol) is merely adsorbed on the external surface but not intercalated into the interlayer space. In temperature scan experiments, water sorption leads to the dielectric permittivity/loss hysteresis loops, where the values upon cooling are unusually larger than those upon heating. In frequency scan experiments, multiple frequency- and temperature-dependent anomalies are detected. The AC conductivity was fitted to the Jonscher universal power law response (σ′AC = σDC + Aωs) from 101 to 106 Hz and 400–25 °C. We observed an uncommon U-shaped A(T) but an inverted U-shaped s(T), regardless of the interlayer ion, charge per formula unit, or pellet density. These plots allow a qualitative description of (i) the apparent activation energy, (ii) the effective dimension of the conduction pathway, and (iii) the charge carrier concentration, all as a function of the temperature under the influence of atmospheric water. Our physical interpretation is potentially applicable to other systems, providing insights into the (unintentional) water-induced conductions and complementing rigorous but time-consuming investigations by controlled humidity experiments.

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