Study of Pr-doped Ceria-based Electrolytes for IT-SOFC
Date Issued
2006
Date
2006
Author(s)
Chen, Mei-Ju
DOI
zh-TW
Abstract
Pr-doped ceria-based electrolyte for intermediate temperature solid oxide fuel cell (IT-SOFC) was successfully synthesized by Pechini process (citric acid process). All the Pr-doped ceria (CPO) of the formula Ce1-xPrxO2-δ where x = 0.05-0.35 and those co-doped with alkaline earth of the formula Ce0.7Pr0.3-yMyO2-δ, 0.01 ≦ y ≦0.05 were ceria based solid solutions of fluorite type structures, characterized by X-ray powder diffraction. A portion of Pr3+ ions doped in ceria was oxidized to Pr4+ during the calcination process at 700℃ in air. Compared with the Pr LⅢ-edge X-ray absorption near-edge spectroscopy (XANES) profiles of Pr2O3 and Pr6O11, all the XANES profiles of the Pr-doped ceria materials after calcination at 1500℃ in air were similar to that of Pr6O11. As a result, lower number of oxygen vacancies was created in the samples than that expected from the original doping ratios.
The ionic conductivities of the Pr-doped ceria-based materials were measured at 400-700℃ in air by using AC impedance spectroscopy. In the CPO system, Ce0.7Pr0.3O2-δ (30CPO) gave the highest conductivity of 0.0668 Scm-1, which was higher than 0.0316 Scm-1 for Ce0.8Gd0.2O2-δ (CGO) and 0.041 Scm-1 for Ce1-xSmxO2-δ (CSO), and the latter two were reported to give the highest conductivities among ceria-based materials applied in IT-SOFC.
The effect of co-doping of alkaline earth in CPMO system on ionic conductivity was also investigated. Compared with CPO, it was found that Mg2+-dopant had positive improvement in conductivity, but the Ca2+-dopant did not. The material doped with small amount of Mg2+, Ce0.7Pr0.28Mg0.02O2-δ was found to retain the unit cell dimension as that of 30CPO and gave the highest conductivity.
Subjects
固態氧化物燃料電池
氧化鈰電解質
氧離子導體
SOFC
doped ceria
oxygen ion conductor
Type
thesis
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