On the conduction pathway for protons in nanocrystalline yttria-stabilized zirconia

Abstract

In this communication we elucidate a microstructural picture of proton conduction in nano-crystalline yttria-stabilized zirconia at low temperatures (Kim et al. Adv. Mater., 2008, 20, 556). Based on careful analysis of electrical impedance spectra obtained from samples with grain sizes of approximately 13 and approximately 100 nm under both wet and dry atmospheres over a wide range of temperatures (room temperature-500 degrees C), we were able to identify the pathway for proton conduction in this material. It was found that the grain boundaries in nano-crystalline yttria-stabilized zirconia are highly selective for ion transport, being conductive for proton transport but resistive for oxygen-ion transport.

1H-NMR measurements of proton mobility in nano-crystalline YSZ

“…This finding indicates that the protons contributing to peak 2 belong in fact to mobile protons, in accordance with the reported proton conductivity in nanocyrstalline YSZ. 5,6,14 Fig. 4b shows the spectra at 32 1C before and after the heating procedure.…”

“…This has been attributed to proton conduction. 5 While this phenomenon only occurs in nano-crystalline samples, it is supposed that the enhanced conductivity is based on a grain-boundary mechanism, 6 or transport along internal interfaces and nanopores. 7 We use 1 H-NMR to clarify the transport mechanism of protons incorporated into the dense, nano-crystalline samples.…”

Colossal resistance switching and band gap modulation in a perovskite nickelate by electron doping

“…Above it, yttria-stabilized zirconia (YSZ) is deposited to serve as a gate insulator at device operation temperature. The low proton conductivity in YSZ at room temperature makes it a good barrier to prevent protons leaving from BYZ/SNO gate stacks during device operation at 20°C; its relatively high proton conductivity at elevated temperature makes it possible to inject protons through the Pd gate electrode into BYZ/SNO layers at elevated temperature 28 . On YSZ, Pd gate electrode serves as both excellent proton conductor and catalyst for hydrogen dissociation 29 .…”

Unusual decrease in conductivity upon hydration in acceptor doped, microcrystalline ceria

“…Proton solubility in pure and doped ceria and zirconia has been investigated by secondary ion mass spectrometry 9,10 and shown to be higher in polycrystalline samples than single crystals. 9 In addition, water uptake in the grain boundary regions of nanostructured doped ceria [11][12][13][14][15] and zirconia 14,16,17 has been shown to dominate ionic transport at temperatures below B150 1C. This intriguing result motivates a quantitative exploration of the limits of the influence of water on the properties, particularly grain boundary properties, of doped ceria with dopant concentrations and microstructure relevant to applications as solid electrolytes and electrodes.…”