| Summary: | 碩士 === 元智大學 === 化學工程與材料科學學系 === 105 === In this study, a novel yttrium-doped SrTiO3 anode is developed to substitute Ni / YSZ (Yttria Stabilized Zirconia) anode that commonly used in Solid oxide fuel cells (SOFCs). The characterizations was done to compare the performance and electrochemical properties of the material with the conventional one.
YxSr1-xyTiO3-δ (0.06≤"x"≤0.09, y=1.0, 1.5, 2.0) are prepared by citric-EDTA acid method. The as-synthesized powder was characterized by using X-Ray Diffraction (XRD), X-ray Fluorescence Spectrometer (XRF), four poles conductivity measurement, Field Emission scanning electron microscope (FE-SEM) and thermal mechanical analyzer (TMA).
The XRD pattern shows that the YST powder was successfully synthesized under reducing atmosphere by using this method. The pure phase of YST peaks can be found as the main phase on the XRD result. However, a small trace amount of Y2Ti2O7 impurities was still can be identified in the material. The comparison of the XRD results of different ratio of Yttrium also has been done. The lattice parameter of the material shows that the volume of the material decreases at low doping rate and then slowly increase as the increase of contents of Yttrium.
The samples was calcine in Ar : H2 (96:4) atmosphere at temperature of 1300 °C. The electrical conductivity of YxSr1-xyTiO3-δ was then measured at 800 °C. The results shows that Y0.08Sr0.84TiO3-δ exhibits the highest conductivity of 54 Scm-1. The thermal expansion also measured using TMA. The CTE value of YxSr1-xyTiO3-δ (0.06≤"x"≤0.09, y=1.5, 2.0) are in the range of 10.04×10-6K-1 ~ 12.28×10-6K-1. This proof that the composite materials had better matching CTE with YSZ.
The phase stability of Y0.08Sr0.92TiO3-δ, Y0.07Sr0.895TiO3-δ and Y0.08Sr0.84TiO3-δ were also investgated by putting the material in syngas atmosphere (25% H2 / 5% CH4 / 30% CO / 40% CO2) at 850 oC. The sample was putted through different time range (t = 6, 12, 18, 24, and 30 h) and characterized by using XRD. The XRD results shows that the peak intensity and position of the YST does not show any significant change comparing with untreated samples. Hence, it can be concluded that there is no secondary phase was observed even after 30 h of treatment. This results proof that YST is showing an excellent stability even in reducing atmosphere and high temperature. Therefore, YST has shown a great potential to be substitute anode material for solid oxide fuel cells.
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