Long Term Stability of SOFC with Sc Doped Zirconia
                                                Electrolyte

Herbstritt, Dirk

doi:10.1149/200116.0349pv

Cited by 3 publications

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“…But, recently the long-term cell testing 10 mol% Sc 2 0 3 (10 SSZ) electrolyte was demonstrated byHerbstritt et al 2001 …”

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confidence: 99%

Materials for Solid Oxide Fuel Cells

Basu

Recent Trends in Fuel Cell Science and Technology

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The components of a single cell are electrolyte, cathode and anode. When single cells are stacked together to generate useful power, then it requires two more cell components, viz. interconnect and sealant. As mentioned in previous section, the electrodes (cathode and anode) must have mixed electronic/ionic conductivity and matching thermal expansion with electrolyte and interconnect. The electrolyte must have very high ionic conductivity and capable of withstanding both oxidizing and reducing environment down to 10~1 8 atm at high operating temperature. Interconnect must be an electronic conductor and have similar characteristics to that of electrolyte. A sealant needs to fulfill all the above mentioned criteria for all the above cell components. An overview of the existing and alternate cell component materials for electrolyte, cathode, anode, interconnect and sealant are given in this section. A brief description on the preparation of such cell components are also given. ElectrolytesElectrolyte is considered as the main component of the ceramic fuel cell whose general requirements have already been mentioned in the previous section. Over the years many electrolytes have been developed. During this period, through detailed basic and fundamental studies on structure-property relationship of these electrolytes, a strong understanding has been developed. The electrolyte may carry either oxide-ion (0 2~) or proton (H + ). In this section both types of conductors are discussed. Detailed information on these electrolytes is available in several literatures/books (Subbarao 1984, Strickler et al. Oxide-ion conductors are best categorized in the following structural groups: Fluorite-based (Zr0 2 , Ce0 2 ); 8-Bi 2 0 3 and doped Bi 2 0 3 ; Perovskites-doped LaGa0 3 ; Brownmillerites-Ba 2 Ln 2 0 5 ; Pyrochlores-Gd 2 Zr 2 0 7 , Gd 2 Ti 2 0 7 and rare earth-based Apatites-La 9 Sr!Si 6 0 26 5 . Zr0 2Eight mol% of Y 2 0 3 stabilized Zr0 2 , commonly known as YSZ or 8YSZ, is the most widely used electrolyte for SOFC which fulfills almost all the criteria for an electrolyte. It is a well studied material and showed extremely good performance as SOFC electrolyte in several demonstration units of Westinghouse which are running for several years . Choudhary et al. (1980) studied the phase diagram and defect structures of various fluorite structures including Zr0 2 -Y 2 0 3 system. Zirconia in its pure form has three polymorphs. From room temperature monoclinic structure it changes to a tetragonal phase above 1170°C and finally to a cubic fluorite structure above 2370°C which exists up to the melting point of 2680°C. These transformations are martensitic in nature and are reversible. There is also about 4% volume change reported during monoclinic to tetragonal phase transformation. However, the tetragonal or cubic phase can be stabilized at room temperature by direct substitution of small amount of divalent or trivalent cations at the host lattice (Zr 4+ ). The common dopants for zirconia are Y 2 0 3 , Yb 2 0 3 , Sc 2 0 3 , Gd 2 0 3...

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“…But, recently the long-term cell testing 10 mol% Sc 2 0 3 (10 SSZ) electrolyte was demonstrated byHerbstritt et al 2001 …”

mentioning

confidence: 99%

Materials for Solid Oxide Fuel Cells

Basu

Recent Trends in Fuel Cell Science and Technology

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Macroscale modeling of cathode formation in SOFC

Ivers-Tiffée

Weber

Schmid³

et al. 2004

Solid State Ionics

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Equivalent Circuit Model Analysis of Microstructure-Controlled LSM/ScSZ Composite Cathodes by Powder Slurry Impregnation Method

Shimada

Takizawa

Michibata

et al. 2014

J. Electrochem. Soc.

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Improved electrochemical performance of strontium-doped lanthanum manganite (LSM)/scandia-stabilized zirconia (ScSZ) composite cathodes for solid oxide fuel cells was accomplished by using the powder slurry impregnation (PSI) method where a prefabricated thin porous ScSZ electrolyte layer is impregnated with LSM/ScSZ powder mixture in slurry. The PSI method enabled control of the electrolyte surface roughness, resulting in a decreased electrode polarization resistance despite a tendency of the ohmic resistance to increase due to the added porous ScSZ electrolyte layer. Resistance separation by electrochemical impedance spectroscopy with an equivalent circuit model (ECM) revealed that the proposed composite cathodes exhibited a significant reduction in the oxygen reduction reaction (ORR) resistance at the triple-phase boundary (TPB). Optimization of the electrolyte surface structure is therefore critical so as not to offset the improvement in the ORR resistance. Furthermore, besides the ECM used to separate the resistances, two ECMs that represent the microstructure of actual composite electrodes were evaluated to clarify the electrode structural factors determining the measured impedance spectra. The analysis revealed that impedance response is influenced by the area ratio of the double-phase boundary to the TPB, although cathode performance is mainly determined by the TPB area and the ionic conduction resistance within composite electrodes.

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Long Term Stability of SOFC with Sc Doped Zirconia Electrolyte

Cited by 3 publications

References 0 publications

Materials for Solid Oxide Fuel Cells

Materials for Solid Oxide Fuel Cells

Macroscale modeling of cathode formation in SOFC

Equivalent Circuit Model Analysis of Microstructure-Controlled LSM/ScSZ Composite Cathodes by Powder Slurry Impregnation Method

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