Fabrication and Characterization of Functionally Graded Cathodes Based on in-situ Formed La0.6Sr0.4CoO3-δ for Intermediate Temperature SOFCs

doi:10.3724/SP.J.1077.2014.13458

Abstract

Abstract:

Precursor powders of La_0.6Sr_0.4CoO_3-δ (LSC) and composite powders of LSC precursor and Ce_0.8Gd_0.2O_2-_δ (CGO) were prepared by Sol-Gel process. The precursor powders of LSC were characterized by TGA, XRD, BET and exhibited homogeneity and high specific surface area. XRD analysis indicated that single phase of LSC can be formed after calcination at high temperature in Ar and annealing at 850℃ for 2 h in air, which corresponds to the fabrication and annealing condition of functionally graded cathode before SOFC stack operation. Functionally graded cathode of LSC/CGO precursor and LSC precursor were sintered at 900--1000℃ in Ar, which were deposited on NiO/YSZ anode supported half cell with YSZ as electrolyte layer and CGO as barrier layer. Microstructural analysis by SEM and EDX indicated that graded cathode contacted well with CGO layer. It was found that SrZrO₃ was formed at the YSZ-CGO boundary. The test of single SOFC cells with in-situ formed LSC showed that cell performance was improved with decrease of the sintering temperature. In comparison, the best cell performance was achieved at the sintering temperature 900℃.

Key words: solid oxide fuel cell, gradient cathode, LSC, in-situ formation

CLC Number:

TQ174

GUO Mi-Lan, TU Heng-Yong, LI Si-Lin, YU Qing-Chun. Fabrication and Characterization of Functionally Graded Cathodes Based on in-situ Formed La_0.6Sr_0.4CoO_3-_δ for Intermediate Temperature SOFCs[J]. Journal of Inorganic Materials, 2014, 29(6): 621-626.

Figures/Tables 8

Fig. 1 TG curve of La0.6Sr0.4CoO3-δ precursors

Fig. 2 XRD patterns of LSC after 900℃ (a), 950℃ (b) and 1000℃ (c) heat treatments

Fig. 3 I-V-P curves of single cells at 800℃ with graded cathodes sintered at different temperatures in Ar

Fig. 4 I-V-P curves of single cell at different temperatures

Fig. 5 Electrochemical impedance spectra of SOFC measured at different temperatures

Fig. 6 SEM images of cross-section of the single cell (a) and surface of cathode (b) (sintering temperature: 900℃)

Fig. 7 Locations in YSZ-CGO interface layer for EDX analysis

Table 1 Elements at location “2”

Element	wt%	at%
Sr	0.56	0.91
Zr	1.88	2.91
Ce	79.42	79.92
Gd	18.14	16.26

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