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Journal of ELECTRONIC MATERIALS, Vol. 46, No. 4, 2017
DOI: 10.1007/s11664-016-5268-9
2017 The Minerals, Metals & Materials Society
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Web End = Effect of Strontium-Doped Lanthanum Vanadate on Crystal Structure, Conductivity and Vanadium Valence Stateof a La1 xSrxVO3 Anode in a Reducing Environment
CHI-YANG LIU,1,3 SHU-YI TSAI,1 CHUNG-TA NI,1 and KUAN-ZONG FUNG1,2
1.Department of Materials Science and Engineering, National Cheng Kung University, No. 1, Ta-Hsueh Road, Tainan 70101, Taiwan. 2.Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan, Taiwan. 3.e-mail: [email protected]
La1 xSrxVO3 (where x = 0, 0.1, 0.3, 0.5, 0.7, and 1) exhibits a transition from
an antiferromagnetic insulator to a paramagnetic metallic conductor and has been synthesized as a potential anode material for solid oxide fuel cells (SOFCs). La1 xSrxVO3 was synthesized by a solid-state reaction process fol
lowed by heat treatment under a reducing atmosphere (Ar:80/H2:20). X-ray diffraction (XRD) results indicate that LaVO3 was substituted with various amounts of Sr2+ in the cation sublattice. Pure LaVO3 shows an orthorhombic structure. After Sr2+ substitution, a more symmetrical cubic perovskite structure was obtained because the tolerance factor is close to 1. The valence state of the vanadium ions of the La1 xSrxVO3 was further veried by x-ray
photoelectron spectroscopy (XPS). According to the XPS results, when the lanthanum ion was substituted by a strontium ion, the negatively charged defect, SrLa, was compensated for by changing the valence of vanadium from a trivalent to a tetravalent or pentavalent state. The dependence of conduction behavior of La1 xSrxVO3 on the amount of Sr addition is discussed in terms of
the hopping process with super/double exchange interaction and a charge transfer mechanism.
Key words: Intermediate-temperature SOFC, anode, La1 xSrxVO3,
conductivity, XPS
INTRODUCTION
Solid oxide fuel cell (SOFCs) are one of the most important power generation technologies because of their high-energy conversion efciency, low noise, and low pollution. SOFCs are normally operated between 800 C and 1000 C.1,2 A nickel (Ni) cermet (mixture of ceramic and metal) is a commonly used material for the anode of SOFCs since Ni provides high electronic conductivity, reasonably good high-temperature stability, and high catalytic activity. The high operating temperature (1073 K) of SOFCs
provides exibility in choice of fuel. Typically, hydrocarbons are reformed upstream...