Title page for etd-0729108-043843


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URN etd-0729108-043843
Author Ching-Shiung Hsu
Author's Email Address d9036804@student.nsysu.edu.tw
Statistics This thesis had been viewed 5336 times. Download 647 times.
Department Materials Science and Engineering
Year 2007
Semester 2
Degree Ph.D.
Type of Document
Language English
Title A study of deposition and electrochemical performance of cathode films for intermediate temperature solid oxide fuel cell
Date of Defense 2008-06-18
Page Count 202
Keyword
  • cathode films
  • electrochemical performance
  • solid oxide fuel cell
  • Abstract In this study, deposition of La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) oxide films on Gd-doped ceria (CGO) substrates by an electrostatic assisted ultrasonic spray pyrolysis (EAUSP) method was demonstrated for the first time. The electrostatic field employed for directing the aerosol stream towards the substrate was shown to be indispensable for film deposition. The XRD result indicates that a single phase of cubic perovskite was obtained in the calcined films. SEM examination reveals that the electric field strength had a profound effect on film porosity with weaker field resulting in higher porosity. The results of impedance measurement on LSCF//CGO//LSCF cells indicate that the area specific resistance (ASR) values of current LSCF films and their activation energies are comparable to that obtained by conventional sample preparation routes. In view of the simplicity, efficiency and economy of film deposition and the sound electrochemical characteristics of the obtained films manifested in current work, it is concluded that EAUSP method is a promising method for preparation of SOFC electrode films.
    Besides the EAUSP method, electrostatic spray deposition (ESD) method was also employed to deposit LSCF films. The growth mechanism of LSCF films deposited on silicon wafer was studied by examining a series of films obtained with increasing deposition durations. The results show that the film formation mechanism in the initial stage depends on the deposition temperature, and films with a unique porous structure were obtained when a deposition temperature lower than the boiling point of the precursor solution was used.
    Deposition parameters were also varied systematically to deposit LSCF cathode films on CGO substrates to obtain symmetrical cells. The microstructure and morphology of obtained films were investigated by X-ray diffraction and SEM, and the area specific resistances of the symmetrical cells measured by electrochemical impedance spectroscopy (EIS). The minimum interfacial ASR value associated with the LSCF cathodes was 0.25 ohm•cm2 at700 °C.
    NiO-SDC (Sm0.2Ce0.8O1.9)/SDC/LSCF (La0.6Sr0.4Co0.2Fe0.8O3-δ) cells with either single
    layer or double layer cathode were also fabricated and tested. The single layer LSCF cathode
    was made by stencil printing while the double layer one was prepared by depositing a thin
    porous layer on the SDC electrolyte by ESD before stencil printing LSCF. The maximum
    power density increased from 1.04 to 1.18 Wcm-2 at 700°C when the LSCF inter-layer was
    introduced. The results showed that the ASRs of the cells reduced to half with the addition of
    the LSCF inter-layer.
    Advisory Committee
  • Tzu-Chien Hsu - chair
  • Bae-Heng Tseng - co-chair
  • S. J. Bai - co-chair
  • Hong-Yang Lu - co-chair
  • Jenn-Shing Chen - co-chair
  • H.-J. Huang - co-chair
  • Bing-Hwai Hwang - advisor
  • Files
  • etd-0729108-043843.pdf
  • indicate access worldwide
    Date of Submission 2008-07-29

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