Structure and Electrochemical Behavior of Plasma-Sprayed LSGM Electrolyte Films
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Structure and Electrochemical Behavior of Plasma-Sprayed LSGM Electrolyte Films H. Zhang1, X. Ma2, J. Dai1, S. Hui2, J. Roth1, T.D. Xiao1, and D.E. Reisner1 1. US Nanocorp, Inc, 74 Batterson Park Road, Farmington, CT 06032, U.S.A. 2. Inframat Corporation, 74 Batterson Park Road, Farmington, CT 06032, U.S.A. ABSTRACT An intermediate temperature solid oxide fuel cell (SOFC) electrolyte film of La0.8Sr 0.2Ga0.8Mg0.2O2.8 (LSGM) was fabricated using a plasma spray process. The microstructure and phase were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical behavior of the thermal sprayed LSGM film was investigated using electrochemical impedance spectroscopy (EIS). The study indicates that thermal spray can deposit a dense LSGM layer. It was found that the rapid cooling in the thermal process led to an amorphous or poor crystalline LSGM deposited layer. This amorphous structure has a significant effect on the performance of the cell. Crystallization of the deposited LSGM layer was observed during annealing between 500-600 oC. After annealing at 800 oC, the ionic conductivity of the sprayed LSGM layer can reach the same level as that of the sintered LSGM. INTRODUCTION Seeking efficient, economical and advanced fabrication procedures for intermediate temperature SOFC has become one of the key factors to successfully develop integrated SOFCs with high performance, high power density, long service life and low cost. Currently, only a few processing approaches exist in fabricating SOFCs, including electrostatic spray deposition [1], sputter deposition [2], electroless deposition [4], slip casting (SL), and tape casting and calendaring [5]. Disadvantages of these processing techniques include low processing efficiency, complicated processes, and high cost. In this study, a plasma spray approach has been introduced to fabricate electrolyte and electrode layers separately and total-cells consisting of anode/electrolyte/cathode via a sequential plasma spray deposition process in a single operation. In this process, La0.8Sr0.2MnO3 (LSM) was selected as the material for cathode and Sr0.88Y0.08TiO3 (SYT) as the anode material. The electrolyte layer of LSGM was used in plasma spray based on the requirement of a SOFC with operation temperature of 500 – 800oC. The electrolyte layer chemistry and physical properties are very important in SOFC studies. Its ionic conductivity should be high enough at working temperature range, i.e. 0.16 S/cm for LSGM at 800 oC. Also it should be a condensed layer to isolated fuel and air effectively and any cell leakage should be avoided in the cell. This study is to explore the use of an integrated thermal spray technique for the preparation of an LSGM electrolyte layer and explore its electrochemical performance. EXPERIMENTAL Thermal spray La0.80Sr0.20Ga0.80Mg0.20O2.80 (LSGM) feedstock was obtained from Praxair. A LSGM disk with a diameter of 13 mm and a thickness of 550 um was fabricated using a plasma
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thermal spray method. In or
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