Surface enhancement of oxygen exchange and diffusion in the ionic conductor La2Mo2O9

Abstract

Isotopic surface oxygen exchange and its subsequent diffusion has been measured using secondary ion mass spectrometry in the fast ionic conductor La 2 Mo 2 O 9 . A silver coating was applied to the sample surface to enhance the surface exchange process for dry oxygen.Contrary to previous studies performed using a wet atmosphere, no grain boundary diffusion tail was observed under these optimized dry exchange conditions. The activation energy for oxygen diffusion was found to be 0.66(±0.09) eV at high temperature (>570˚C), and 1.25(±0.01) eV at low temperature (<570˚C). Time-of-Flight secondary ion mass spectrometry was employed to investigate the correlation between the silver coating and the 18 O concentration on the sample surface. A close correlation between the presence of silver and oxygen incorporation on the surface was observed.

Effect of silver addition on the microstructures and electrical responses of La(1.7)Sr(0.3)Mo(2)O(9−δ) ceramics

“…This may result from silver evaporation at the high temperatures. There are no impurity peaks found in XRD diffraction patterns, indicating that the silver is chemically stable in La 2 Mo 2 O 9 despite the relatively high anneal temperature, which is in agreement with previously reported [18]. In Fig.…”

“…As well, silver has been noted as a good catalyst for the electrochemical reduction of oxygen in Ag/electrolyte systems. The application of silver to enhance the surface oxygen exchange for diffusion in ionic conductors has already been demonstrated [16][17][18]. As previous study, the Sr doping in LMO has a positive influence on oxide ion conductivity.…”

Oxygen surface exchange and diffusion studies of La2Mo2O9 in different exchange atmospheres

“…The La 2 Mo 2 O 9 pellets were then polished using diamond suspensions of different grades to a finish of 0.25 μm in order to obtain a shiny flat surface for oxygen isotopic exchange. The samples for dry exchange were then coated with silver (~100 nm) using an Emitech K575X Sputter Coater [13].…”

“…For this work, a silver surface coating was introduced because it has been shown to be effective in improving the oxygen dissociation at the surface [13]. Using this method, the oxygen diffusion profiles within La 2 Mo 2 O 9 for different temperatures in a dry 18 O 2 atmosphere and a H 2 18 O vapor atmosphere were obtained.…”

Application of combined neutron diffraction and impedance spectroscopy for in-situ structure and conductivity studies of La2Mo2O9

“…La 2 Mo 2 O 9 powder was synthesized by the solid state route, which has been detailed in a previous report [9]. To measure AC impedance spectra a dense pellet sample is needed and to ensure that the neutron beam can penetrate the entire sample with good data statistics a larger sample is required.…”