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Title: Oxygen Exchange Kinetics of Epitaxial PrBaCo2O5+delta Thin Films

Abstract

The oxygen exchange kinetics of thin films of the oxygen-deficient double perovskite PrBaCo{sub 2}O{sub 5+{delta}} (PBCO) have been determined by electrical conductivity relaxation (ECR) and by oxygen-isotope exchange and depth profiling (IEDP). Microstructural studies indicate that the PBCO films, prepared by pulsed laser deposition, have excellent single-crystal quality and epitaxial nature. The ECR and IEDP measurements reveal that the PBCO films have high electronic conductivity and rapid surface exchange kinetics, although the ECR data indicate the presence of two distinct kinetic pathways. The rapid surface kinetics compared with those of other perovskites suggest the application of PBCO as a cathode material in intermediate-temperature solid oxide fuel cells.

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
914240
Report Number(s):
BNL-78808-2007-JA
Journal ID: ISSN 0003-6951; APPLAB; TRN: US200809%%113
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Appl. Phys. Lett.; Journal Volume: 88; Journal Issue: 2
Country of Publication:
United States
Language:
English
Subject:
30 DIRECT ENERGY CONVERSION; CATHODES; DEPOSITION; ELECTRIC CONDUCTIVITY; KINETICS; LASERS; OXYGEN; PEROVSKITE; PEROVSKITES; RELAXATION; SOLID OXIDE FUEL CELLS; THIN FILMS; national synchrotron light source

Citation Formats

Kim,G., Wang, S., Jacobson, A., Yuan, Z., Donner, W., Chen, C., Reimus, L., Brodersen, P., and Mims, C. Oxygen Exchange Kinetics of Epitaxial PrBaCo2O5+delta Thin Films. United States: N. p., 2006. Web. doi:10.1063/1.2163257.
Kim,G., Wang, S., Jacobson, A., Yuan, Z., Donner, W., Chen, C., Reimus, L., Brodersen, P., & Mims, C. Oxygen Exchange Kinetics of Epitaxial PrBaCo2O5+delta Thin Films. United States. doi:10.1063/1.2163257.
Kim,G., Wang, S., Jacobson, A., Yuan, Z., Donner, W., Chen, C., Reimus, L., Brodersen, P., and Mims, C. Sun . "Oxygen Exchange Kinetics of Epitaxial PrBaCo2O5+delta Thin Films". United States. doi:10.1063/1.2163257.
@article{osti_914240,
title = {Oxygen Exchange Kinetics of Epitaxial PrBaCo2O5+delta Thin Films},
author = {Kim,G. and Wang, S. and Jacobson, A. and Yuan, Z. and Donner, W. and Chen, C. and Reimus, L. and Brodersen, P. and Mims, C.},
abstractNote = {The oxygen exchange kinetics of thin films of the oxygen-deficient double perovskite PrBaCo{sub 2}O{sub 5+{delta}} (PBCO) have been determined by electrical conductivity relaxation (ECR) and by oxygen-isotope exchange and depth profiling (IEDP). Microstructural studies indicate that the PBCO films, prepared by pulsed laser deposition, have excellent single-crystal quality and epitaxial nature. The ECR and IEDP measurements reveal that the PBCO films have high electronic conductivity and rapid surface exchange kinetics, although the ECR data indicate the presence of two distinct kinetic pathways. The rapid surface kinetics compared with those of other perovskites suggest the application of PBCO as a cathode material in intermediate-temperature solid oxide fuel cells.},
doi = {10.1063/1.2163257},
journal = {Appl. Phys. Lett.},
number = 2,
volume = 88,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • Fluctuation analysis in the limit of high magnetic fields was performed on three epitaxial thin films of YBa[sub 2]Cu[sub 3]O[sub 7[minus][delta]] for various oxygen deficiencies [delta][lt]0.3. On the 90-K plateau, the three-dimensional (3D) limit yielded an [ital H][sub [ital c]2]([ital T]) slope of [minus]1.7 T/K for [ital H][parallel][ital c], consistent with previous observations of transport and magnetic properties. Moreover, the 3D scaling showed better convergence than the 2D scaling, which gave relatively low values of [ital H][sub [ital c]2]. In contrast, the transitions were not adequately described by either scaling for [ital T][sub [ital c]] off the 90-K plateau; itmore » is speculated that this is due to an extrinsic broadening of the transitions, possibly due to the lack of a complete percolation path of the ortho-[ital I] phase ([delta]=0).« less
  • Strong correlations between the Hall coefficient [ital R][sub [ital H]], the transition temperature [ital T][sub [ital c]], and the critical current density [ital J][sub [ital c]] were established in a series of epitaxial YBa[sub 2]Cu[sub 3]O[sub 7[minus][delta]] thin films as a function of oxygen deficiency [delta]. Steady increases in [ital R][sub [ital H]] with [delta] suggest that deoxygenation reduces the density of states which, according to BCS theory, should lead to corresponding decreases in [ital T][sub [ital c]]. In contrast, two well-known plateaus occurring at 90 K and 60 K were observed in [ital T][sub [ital c]] vs [delta]. Othersmore » have ascribed these plateaus to either electronic phenomena or phase separations. We find that in the 90-K plateau, the critical current density [ital J][sub [ital c]]([delta],[ital H]=0) decreases with [delta] and extrapolates toward zero at the edge of the plateau, while the relative-field dependence of [ital J][sub [ital c]]([delta],[ital H]) and the flux-creep pinning energies are independent of [delta]. These observations suggest that the phase-separation scenario occurs on the 90-K plateau. However, electronic origins cannot be ruled out at present due to difficulties in determining the equilibrium superconducting properties of oxygen-deficient YBa[sub 2]Cu[sub 3]O[sub 7[minus][delta]] films.« less
  • Superconducting Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} thin films ({Tc}{approximately}85K) were prepared on off-c-axis (001) SrTiO{sub 3}, substrates by pulsed laser deposition. High quality oriented film growth with a c-axis inclined with respect to the surface normal by a tilt angle {alpha} is found up to {alpha} {approximately} 15{degree} from SEM, XRD and resistivity measurements. Isothermal oxygen diffusion is monitored by in-situ electrical resistance measurements at temperatures ranging from 200 C--400 C. From the temporal evolution of the resistance the in-plane diffusion constant D{sub ab} is determined.
  • Samaria-doped ceria (SDC) thin films are particularly important for energy and electronic applications such as micro-solid oxide fuel cells, electrolysers, sensors and memristors. In this paper we report a comparative study investigating ionic conductivity and surface reactions for well-grown epitaxial SDC films varying the samaria doping concentration. With increasing doping above 20 mol% of samaria, an enhancement in the defect association was observed by Raman spectroscopy. The role of such defect associates on the films` oxygen ion transport and exchange was investigated by electrochemical impedance spectroscopy and electrochemical strain microscopy (ESM). The measurements reveal that the ionic transport has amore » sharp maximum in ionic conductivity and drop in its activation energy down to 0.6 eV for 20 mol% doping. Increasing the doping concentration further up to 40 mol%, raises the activation energy substantially by a factor of two. We ascribe the sluggish transport kinetics to the "bulk" ionic-near ordering in case of the heavily doped epitaxial films. Analysis of the ESM first order reversal curve measurements indicate that these associated defects may have a beneficial role by lowering the activation of the oxygen exchange "surface" reaction for heavily doped 40 mol% of samaria. We reveal in a model experiment through a solid solution series of samaria doped ceria epitaxial films that the occurrence of associate defects in the bulk affects the surface charging state of the films to increase the exchange rates. Lastly, the implication of these findings are the design of coatings with tuned oxygen surface exchange by control of bulk associate clusters for future electro-catalytic applications.« less
  • No abstract prepared.