Abstract
Rare earth silicate apatites are one-dimensional channel
structures that show potential as electrolytes for solid oxide fuel cells
(SOFC) due to their high ionic conductivity at intermediate temperatures
(500−700 °C). This advantageous property can be attributed to the
presence of both interstitial oxygen and cation vacancies, that create
diffusion paths which computational studies suggest are less tortuous and
have lower activation energies for migration than in stoichiometric
compounds. In this work, neutron diffraction of Nd(28+x)/3AlxSi6−xO26
(0 ≤ x ≤ 1.5) single crystals identified the locations of oxygen interstitials,
and allowed the deduction of a dual-path conduction mechanism that is a
natural extension of the single-path sinusoidal channel trajectory arrived at
through computation. This discovery provides the most thorough understanding of the O2− transport mechanism along the
channels to date, clarifies the mode of interchannel motion, and presents a complete picture of O2− percolation through apatite.
Previously reported crystallographic and conductivity measurements are re-examined in the light of these new findings.
structures that show potential as electrolytes for solid oxide fuel cells
(SOFC) due to their high ionic conductivity at intermediate temperatures
(500−700 °C). This advantageous property can be attributed to the
presence of both interstitial oxygen and cation vacancies, that create
diffusion paths which computational studies suggest are less tortuous and
have lower activation energies for migration than in stoichiometric
compounds. In this work, neutron diffraction of Nd(28+x)/3AlxSi6−xO26
(0 ≤ x ≤ 1.5) single crystals identified the locations of oxygen interstitials,
and allowed the deduction of a dual-path conduction mechanism that is a
natural extension of the single-path sinusoidal channel trajectory arrived at
through computation. This discovery provides the most thorough understanding of the O2− transport mechanism along the
channels to date, clarifies the mode of interchannel motion, and presents a complete picture of O2− percolation through apatite.
Previously reported crystallographic and conductivity measurements are re-examined in the light of these new findings.
| Original language | English |
|---|---|
| Pages (from-to) | 4468-4483 |
| Journal | Journal of the American Chemical Society |
| Volume | 138 |
| Issue number | 13 |
| Early online date | 25 Mar 2016 |
| DOIs | |
| Publication status | Published - 6 Apr 2016 |