Properties and microstructural analysis of La1-xSrxCoO3-delta (x=0-0.6) cathode materials

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Title:	Properties and microstructural analysis of La1-xSrxCoO3-delta (x=0-0.6) cathode materials
Authors:	Wu, YC (Wu, Yu-Chuan) Huang, PY (Huang, Peng-Yu) Xu, GY (Xu, Guiying)
Contributors:	化材系
Keywords:	Solid oxide fuel cell Sintering Microstructure Electrochemical impedance spectroscopy Transmission electron microscopy
Date:	2017-02
Issue Date:	2017-04-27 13:44:42 (UTC+8)
Abstract:	La1-xSrxCoO3-delta (LSC; x=0-0.6) materials were synthesized and sintered at 1200 degrees C for 6 h by solid-state reaction for use as a cathode material in intermediate-temperature solid oxide fuel cells (IT-SOFCs). Physical property and microstructural analyses of the LSC materials were performed via X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, dilatometer testing, dc four-wire measurement, and ac impedance spectroscopy. The sintered LSC samples with x=0-0.5 and x=0.6 showed rhombohedral and cubic perovskite structures, respectively. LSC with x=0.3-0.6 had a dense structure and no secondary phase was observed. The average grain size was approximately 3.1 mu m for x=0.3 and increased to 10.8 mu m at x=0.6. Grain growth could thus be promoted by Sr ions doping. The LSC samples with x=0 and x=0.3-0.6 respectively exhibited semiconductor-like and metallic-like conduction behavior below 800 degrees C. The LSC (x=0.3-0.5) materials underwent R- to C-phase transformation at 700-750 degrees C. At 550-700 degrees C, the activation energies were in the range of 0.028-0.040 eV for the samples with x=0.3-0.5, while at 700 degrees C, the conductivities were in the range of 2149-2234 S cm(-1). This study found that the La0.6Sr0.4CoO3-delta sample, showing a higher conductivity, is the best material to be used as a cathode for IT-SOFCs (500-700 degrees C). Two super-lattice diffraction spots: 1/2{110}(R) (or 1/2{010}(C)} and 1/2{0 (1) over bar(1) over bar}(R) (or 1/2{00 (1) over bar}(C)) were evident in the La0.6Sr0.4Co3-delta material. This super-lattice structure was induced by clustering and short-range ordering of the dopant Sr ions or oxygen vacancies, and the unit cell was defined as a tetragonal cell with a(C)xa(C)x2a(C). R- and C-phase transformation matrices for the plane indices were also obtained.
Relation:	CERAMICS INTERNATIONAL 卷: 43 期: 2 頁碼: 2460-2470
Appears in Collections:	[Department of Chemical & Materials Engineering] journal articles

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