Investigation of Homogeneity, Phase Transformation and Long-term Conductivity of Nb and Y Co-doped Bi2O3-Based Electrolyte
Date Issued
2011
Date
2011
Author(s)
Dai, Zih-Ting
Abstract
This work synthesized Nb and Y–codoped Bi2O3 materials used as the electrolyte of solid oxide fuel cells. Four objectives (1) improving dispersion of Y2O3 powder, (2) increasing homogeneity of Nb and Y content in the materials, (3) optimizing the ratio of Nb/Y and total doping concentration (TDC), (4) understanding the degradation of long-term conductivity, are investigated. Not only the dispersion and homogeneity were increased by using modified Y2O3 powder, but the conductivity of the samples was also promoted. In sample 21NY(5:2), the standard deviations of Nb and Y content are 0.20 mol% and 0.18 mol%, respectively. Moreover, the method of powder modified by ethanol was also effective on Nb, Er-codoped system. Based on the results of zeta-potential, IR spectrum, and TOC, the dispersion mechanism of Y2O3 in aqueous solution was proposed. The optimal composition in Bi2O3-Nb2O5-Y2O3 system to stabilize δ-phase at room temperature was 12NY(3:1) with 0.07 Scm-1 of short-term conductivity at 650oC. For long-term stability, 21NY(3:1), 15NY(3:1), and 12NY(3:1) showed excellent phase stability, which maintained δ-phase after annealing at 650oC for 800 h. However, 15NY(3:1) has the best long-term conductivity with 60% (0.0196 Scm-1) retention of initial value after 300 h aging. On the other hand, the conductivity decay was governed by the formation of second phase (α’) on the surface. The transference number of 15NY(3:1) was 0.62 at 650oC.
Subjects
Bismuth oxide
SOFC
Long-term conductivity
Transference number
Homogeneity
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-100-R98527047-1.pdf
Size
23.54 KB
Format
Adobe PDF
Checksum
(MD5):a7423f3e816f4ed978496755fdd7aecc