Determination of Oxygen Transport Properties from Flux and Driving Force Measurements

Abstract

We demonstrate that an electrolyte probe can be used to measure the difference in oxygen chemical potential across the surface, when an oxygen flux is forced through an oxygen permeable membrane disk. The oxygen flux as well as the total oxygen chemical potential difference is carefully controlled by an oxygen pump. The developed method is tested on a ͑La 0.

Defect chemistry and oxygen transport of (La0.6Sr0.4−xMx)0.99Co0.2Fe0.8O3−δ, M=Ca (x=0.05, 0.1), Ba (x=0.1, 0.2), SrPart I: Defect chemistry

“…To get data at lower temperatures and high p O 2 the reference T could be set at a lower value. A reduction of T will, however, slow the pumping process considerably as the equilibration of the powder and the gas inside the cell is controlled by surface exchange processes in the powder [5,25] which are thermally activated. The equilibration will also slow down significantly at low p O 2 [5,25], so even at high T, pumping to very low p O 2 is time consuming.…”

“…Other uses of MIECs exist in the field of controlled oxidation, oxygen production, or reactors for partial oxidation of methane to synthesis gas [3,4]. Current research focuses on identifying materials combining good mechanical, catalytic and oxygen permeation properties [5]. A better understanding of membrane materials can facilitate identification of materials with high thermal stability and oxygen permeability.…”

Porous Thick Film Lanthanum Strontium Ferrite Stress and Oxygen Surface Exchange Bilayer Curvature Relaxation Measurements

“…43 For each curvature relaxation, the bilayer samples were held at the new p O 2 for at least 5 times the observed sample relaxation time constant. The Origin software program was used to plot the normalized curvature relaxation data and fit the values of k using Equation 15.…”

“…Using the procedures detailed in Yang, 44 the 2D serial SEM images were aligned, cropped and segmented into binary images. The Mimics software program (Materialize) was then used to 1) create a 3D reconstruction from the 2D images and to 2) determine the V V and S V values needed to extract k using Equation 15. For all the samples, the 25 nm z resolution was less than 1/15 th of the particle size, ensuring 3D reconstruction V V and S V errors less than 5%.…”

“…For instance, chemical oxygen surface exchange coefficient (k) discrepancies greater than 4 orders of magnitude are reported at identical temperature and oxygen partial pressure conditions for the MIEC material La 0.6 Sr 0.4 FeO 3-δ (LSF64). [10][11][12][13] Similarly, large k discrepancies have been observed for other MIEC materials such as lanthanum strontium cobalt iron oxide [14][15][16][17] and reduced cerium oxide. [18][19][20][21] Since recent studies have shown that strain can alter k, 20,21 it is likely that some of these observed k discrepancies are due to differences in MIEC stress state.…”