New buffer layer material La(Pr)CrO 3 for intermediate temperature solid oxide fuel cell using LaGaO 3 -based electrolyt
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Toru Inagaki The Kansai Electric Power Co., Inc., Amagasaki, Hyogo 661-0974, Japan
Shintaro Ida and Tatsumi Ishiharaa) Department of Applied Chemistry, Faculty of Engineering, Kyushu University, Nishi-Ku, Fukuoka 819-0395, Japan (Received 12 January 2012; accepted 21 May 2012)
A metal-supported solid oxide fuel cell (SOFC) using Ce0.8Sm0.2O2 (Sm-doped ceria, SDC) buffer layer and La0.9Sr0.1Ga0.8Mg0.2O3 (LSGM) electrolyte films showed a small degradation in the cell performance after a long-term operation because of La migration from the electrolyte to the buffer layer, resulted in a formation of a less conductive phase. Thus, various ceramic materials such as doped ceria and perovskite-related oxides were investigated for an effective buffer layer with respect to fabricating reliable metal-supported SOFCs using a LSGM electrolyte film. In particular, La-doped CeO2 (LDC) and Pr-doped LaCrO3 (LPCr) were investigated as buffer layer material since the materials showed chemical compatibility with the LSGM and anode materials. The cell using a LDC buffer layer showed a prior stability during the operation for 100 h at 973 K, while the power density of the cell was slightly low owing to the low electrical conductivity of LDC compared with that of SDC or LPCr. In contrast, the cell using a LPCr buffer layer revealed significantly low open circuit voltage (OCV) and power density, which were attributed to Pr decomposition in the LPCr caused by the reactivity with water vapor. However, the metal-supported cell with a multilayer electrolyte film including LSGM/LPCr/SDC layers showed an almost theoretical OCV and reasonably high power density with no degradation after a long-term operation for 100 h at 973 K, suggesting that the LPCr layer effectively prevented La migration and the SDC layer led to avoid the Pr decomposition. Thus, a LPCr is an effective buffer layer material for reliable metal-supported SOFCs using a LSGM electrolyte thin film.
I. INTRODUCTION
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.187
investigations have been focused on the discovery of a new electrolyte material4–22 and the fabrication of a thin electrolyte film15–26 to reduce the electrolyte resistance, which is mainly dominated by low conductivity and large thickness of electrolyte. Among new electrolyte materials, La0.9Sr0.1Ga0.8Mg0.2O3d (LSGM) has been considered as an excellent electrolyte material for intermediate temperature solid oxide fuel cells (IT-SOFCs) because it has high oxide ionic conductivity at intermediate temperatures and high transference number of oxide ions over a wide range of oxygen partial pressures.7–11 However, LSGM electrolyte has some drawbacks such as the reactivity with the electrode materials11,12 and poor mechanical strength compared with that of Y2O3-stabilized ZrO2. We have introduced a Ni–Fe metal-supported SOFC having a thin LSGM electrolyte film to solve the problem for poor mechanical strength, in our previous study.19–24 In addition, we confirmed that the rea
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