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Title: Synthesis and characterisation of vanadium doped alkaline earth lanthanum germanate oxyapatite electrolyte
Authors: Li, Henan
Baikie, Tom
Pramana, Stevin S.
Shin, J. Felix
Slater, Peter R.
Brink, Frank
Hester, James
Wallwork, Kia
White, Timothy John
Keywords: Solid oxide fuel cell
Crystal chemistry
Microscopic structure
Issue Date: 2012
Source: Li, H., Baikie, T., Pramana, S. S., Shin, J. F., Slater, P. R., Brink, F., et al. (2012). Synthesis and characterisation of vanadium doped alkaline earth lanthanum germanate oxyapatite electrolyte. Journal of Materials Chemistry, 22(6), 2658-2669.
Series/Report no.: Journal of materials chemistry
Abstract: The crystal chemistry and oxygen conductivity of vanadium-doped apatites of nominal composition [La8AE2][Ge6−xVx]O26+x/2 (AE = Ca, Sr, Ba; 0 ≤ x ≤ 1.5) were studied to establish their potential as intermediate temperature solid oxide fuel cell (SOFC) electrolytes. Single-phase products obtained for x ≤ 0.5 were found, using a combination of powder synchrotron X-ray and neutron diffraction, to be P63/m apatites. The ionic conductivities extracted by complex impedance spectroscopy showed that small vanadium amendments enhanced oxygen mobility at intermediate temperatures (500–700 °C) by more than one order of magnitude, as the incorporation of V5+ through displacement of Ge4+ is charge balanced with interstitial O2− that improves ionic conduction. The most promising composition was La7.88Ca2Ge5.35V0.65O26.15 that delivered σ = 3.44 × 10−4 S cm−1 at 500 °C. The superstoichiometric oxygen was delocalised, without fixed X-ray or neutron scattering centres. Crystal chemistry systematics demonstrate that the Ca-apatite was superior because the relatively small framework expanded the tunnel through reduced (La/AE)O6 metaprism twisting (φ), ensuring the P63/m symmetry was adopted, which favours the passage of O2− with lower activation energy.
DOI: 10.1039/c1jm13752b
Rights: © 2012 The Royal Society of Chemistry. This is the author created version of a work that has been peer reviewed and accepted for publication by Journal of materials chemistry, The Royal Society of Chemistry. It incorporates referee’s comments but changes resulting from the publishing process, such as copyediting, structural formatting, may not be reflected in this document. The published version is available at: [].
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:MSE Journal Articles

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