On Proton Conductivity in Porous and Dense Yttria Stabilized Zirconia at Low Temperature

Abstract

The electrical conductivity of dense and nanoporous zirconia‐based thin films is compared to results obtained on bulk yttria stabilized zirconia (YSZ) ceramics. Different thin film preparation methods are used in order to vary grain size, grain shape, and porosity of the thin films. In porous films, a rather high conductivity is found at room temperature which decreases with increasing temperature to 120 °C. This conductivity is attributed to proton conduction along physisorbed water (Grotthuss mechanism) at the inner surfaces. It is highly dependent on the humidity of the surrounding atmosphere. At temperatures above 120 °C, the conductivity is thermally activated with activation energies between 0.4 and 1.1 eV. In this temperature regime the conduction is due to oxygen ions as well as protons. Proton conduction is caused by hydroxyl groups at the inner surface of the porous films. The effect vanishes above 400 °C, and pure oxygen ion conductivity with an activation energy of 0.9 to 1.3 eV prevails. The same behavior can also be observed in nanoporous bulk ceramic YSZ. In contrast to the nanoporous YSZ, fully dense nanocrystalline thin films only show oxygen ion conductivity, even down to 70 °C with an expected activation energy of 1.0 ± 0.1 eV. No proton conductivity through grain boundaries could be detected in these nanocrystalline, but dense thin films.

Low-temperature performance of yttria-stabilized zirconia prepared by atomic layer deposition

“…This peculiar low-temperature trend has been reported several times [18e23] but its origin is yet unknown. The proposed explanations so far involve different mechanisms: Chiodelli [22,23]. As observed in our HAADF-STEM images, the present ALD YSZ films consist of columnar grains with intragranular pores, as shown in Figs.…”

Electric double-layer transistors: a review of recent progress

“…Its proton conduction was also studied in bulk ceramics and nanocrystalline film [145,146]. In this process, protons are found to migrate along the YSZ surface or grain boundaries, respectively.…”

Gadolinia Doped Ceria Thin Films Prepared by Aerosol Assisted Chemical Vapor Deposition and Applications in Intermediate‐Temperature Solid Oxide Fuel Cells

“…The cross-plane conductivity of these AA-CVD YSZ thin films has been reported previously and strongly depends on microstructure [26,39]. As indicated by dashed an solid lines in Figure 8, the cross-plane oxygen ion conductivity of nanocrystalline granular YSZ is one to two orders of magnitude lower than that of columnar YSZ due to grain boundary blocking effects [26].…”

“…As indicated by dashed an solid lines in Figure 8, the cross-plane oxygen ion conductivity of nanocrystalline granular YSZ is one to two orders of magnitude lower than that of columnar YSZ due to grain boundary blocking effects [26]. Furthermore, the granular and nanoporous YSZ microstructures have been shown to exhibit higher conductivities than expected for oxygen ion conduction at temperatures below 400 C, which is related to proton conduction over the internal surface in an open atmosphere [39]. The conductivity of the GDC thin films as determined in Figure 6 is also plotted for comparison in Figure 8 (dotted line).…”