Hybrid Grain-Core/Grain Boundary Proton Conductivity in Nanocrystalline La2Ce2O7 Thin Films at 298 - 453K
Year: 2026
Type: preprint
Abstract: La3+ doping of ceria promotes hydration at the site of oxygen vacancy defects and, consequently, also protonic conductivity, thereby positioning fluorite-structured La2Ce2O7 (LCO50) as a promising low temperature (LT, i.e., < 473 K) solid state proton-conducting electrolyte . With mean grain size for polycrystalline LCO50 thin films of ~5 nm by sputter-deposition at 293 K, room temperature total conductivity is measured by impedance spectroscopy to be ~7.5×10-9 S/cm. This is approximately two orders of magnitude higher than that previously measured for highly textured, LCO50 thin films, sputter-deposited at 733 K. Here, experimental evidence is provided that the dominant LT conduction mechanism in nanocrystalline LCO50 thin films is protonic, given the measured total activation energy of 0.396±0.007eV between 373K and 453 K. At these temperatures, the conductivity of the nanocrystalline LCO50 films is approximately independent of the atmospheric relative humidity while change is minimal even under high vacuum. We interpret these properties in terms of a hybrid grain-core/grain-boundary protonic conduction mechanism, in which the grain core acts as a proton reservoir and the grain boundary, as a rapid conduction path. Such a micro-fabrication compatible, solid state protonic conductor offers versatile applications including fuel cells, sensors and battery-run devices.
Source: ChemRxiv
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7214229999