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Magnetron sputtered Gadolina-doped Ceria Diffusion Barriers for Metal-supported Solid Oxide Fuel Cells
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
Technical University of Denmark. (Department of Energy Conversion and Storage)
Danish Technological Institute. (Tribology Centre)
Danish Technological Institute. (Tribology Centre)
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2014 (English)In: Journal of Power Sources, ISSN 0378-7753, Vol. 267, 452-458 p.Article in journal (Refereed) Published
Abstract [en]

Gadolinia-doped ceria (GDC) thin films are deposited by reactive magnetron sputtering in an industrial-scale setup and implemented as barrier layers between the cathode and electrolyte in metal-based solid oxide fuel cells consisting of a metal support, an electrolyte of ZrO2 co-doped with Sc2O3 and Y2O3 (ScYSZ) and a Sr-doped lanthanum cobalt oxide cathode. In order to optimize the deposition of GDC to obtain high electrochemical performance of the cells, the influence of film thickness and adatom mobility is studied. The adatom mobility is varied by tuning the deposition temperature and substrate bias voltage.

A GDC layer thickness of 0.6 µm is found to effectively block Sr diffusion when bias voltage and deposition temperature is tuned to promote dense coatings. The adatom mobility has a large influence on the film density. Low temperature and bias voltage result in underdense column boundaries which function as channels for Sr to diffuse to the GDC-ScYSZ interface. By tuning deposition temperature, bias voltage and film thickness area specific resistances down to 0.34 Ωcm2 are achieved at cell tests performed at an operating temperature of 650 °C.

Place, publisher, year, edition, pages
Elsevier, 2014. Vol. 267, 452-458 p.
Keyword [en]
Physical Vapor deposition (PVD); Solid Oxide Fuel Cell (SOFC); GDC; CGO
National Category
Physical Sciences
URN: urn:nbn:se:liu:diva-102517DOI: 10.1016/j.jpowsour.2014.05.101ISI: 000339601800054OAI: diva2:678650
Available from: 2013-12-12 Created: 2013-12-12 Last updated: 2015-01-13
In thesis
1. Yttria-Stabilized Zirconia and Gadolinia-Doped Ceria Thin Films for Fuel Cell Applications
Open this publication in new window or tab >>Yttria-Stabilized Zirconia and Gadolinia-Doped Ceria Thin Films for Fuel Cell Applications
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Solid oxide fuel cells convert chemical energy directly into electrical energy with high efficiency and low emission of pollutants. However, before fuel cell technology can gain a significant share of the electrical power market, the operation temperature needs to be reduced in order to decrease costs and improve the durability of the cells. Application of thin film electrolytes and barrier coatings is a way of achieving this goal.

In this thesis, I have investigated film growth and microstructure of yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (CGO) thin films deposited by physical vapor deposition. The aim is to make industrially applicable coatings suitable for application in solid oxide fuel cells (SOFCs). For this purpose, the coatings need to be thin and dense. YSZ coatings were prepared by pulsed direct current (DC) magnetron sputtering and high power impulse magnetron sputtering (HiPIMS) in both laboratory- and industrial-scale setups.

Industrial-scale pulsed DC magnetron sputtering of YSZ showed that homogenous coating over large areas was possible. In order to increase film density of the YSZ, HiPIMS was used. By tuning deposition pressure, peak power density and substrate bias voltage it was possible to deposit noncolumnar thin films without voids and cracks as desired for SOFC applications.

CGO coatings were deposited by pulsed DC magnetron sputtering with the purpose of implementing diffusion barriers to prevent reactions between Sr from the SOFC cathode and the electrolyte. A model system simulating a SOFC was prepared by depositing thin CGO and YSZ layers on cathode material. This setup allowed the study of Sr diffusion by observing SrZrO3 formation using X-ray diffraction while annealing. Electron microscopy was subsequently performed to confirm the results. The study revealed Sr to diffuse along column/grain boundaries in the CGO films but by modifying the film thickness and microstructure the breaking temperature of the barrier could be increased.

CGO thin films were implemented in metal-based SOFC and the influence of film microstructure and thickness on the electrochemical performance of the cell was studied. Cell tests showed that an area specific resistance (ASR) down to 0.27 Ωcm2 could be obtained 650 °C with sputtered CGO barrier layers in combination with a lanthanum strontium cobaltite cathode. In comparison a spin-coated CGO barrier resulted in an ASR value of 0.50 Ωcm2. This shows the high effectiveness of the sputtered barrier in obtaining state-of-the-art performance.

In summary, this work provides fundamental understanding of the deposition and growth of YSZ and CGO thins films and proves the prospective of employing thin film barrier coating in order to obtain high-performing SOFCs.  

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. 63 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1564
National Category
Natural Sciences
urn:nbn:se:liu:diva-102513 (URN)10.3384/diss.diva-102513 (DOI)978-91-7519-441-7 (print) (ISBN)
Public defence
2014-02-25, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Available from: 2013-12-12 Created: 2013-12-12 Last updated: 2015-01-13Bibliographically approved

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