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Gadolinium-doped ceria (GDC) (known alternatively as gadolinia-doped ceria, gadolinium-doped cerium oxide (GCO), cerium-gadolinium oxide (CGO), or cerium(IV) oxide, gadolinium-doped, formula Gd:CeO₂) is a ceramic electrolyte used in solid oxide fuel cells (SOFCs). It has a cubic structure and a density of around 7.2 g/cm³ in its oxidised form.^[1] It is one of a class of ceria-doped electrolytes with higher ionic conductivity and lower operating temperatures (<700 °C) than those of yttria-stabilized zirconia,^[2] the material most commonly used in SOFCs. Because YSZ requires operating temperatures of 800–1000 °C to achieve maximal ionic conductivity, the associated energy and costs make GDC a more optimal (even "irreplaceable",^[3] according to researchers from the Fraunhofer Society) material for commercially viable SOFCs.

Structure and properties

Oxygen vacancies are created when gadolinium (a trivalent cation) is introduced into ceria (CeO₂, with Ce in the 4+ oxidation state) or on reduction in CO or H₂.^[1] The high concentration and mobility of the oxide ion vacancies results in a high ionic conductivity in this material. In addition to its high ionic conductivity GDC is an attractive alternative to YSZ as an electrolyte due to low reactivity and good chemical compatibility with many mixed conducting cathode materials.^[4] Dopant levels of Gd typically range from 10% to 20%. The majority of SOFC researchers and manufacturers still favor the use of YSZ over CGO due to YSZ having superior strength and because GDC will reduce at high temperature when exposed to H₂ or CO.^[1]

Synthesis

Methods of synthesis have included precipitation,^[5] hydrothermal treatment, sol-gel, spray pyrolysis technique (SPT),^[6] combustion^[7] and nanocasting^[8] using cerium sources such as cerium nitrate, ceric ammonium nitrate,^[9] cerium oxalate, cerium carbonate and cerium hydroxide.^[8] GDC has been synthesized in such forms as powder, ink, discs, and nanomaterials (including nanoparticle, nanocrystals, nanopowder, and nanowires).^[10]

Applications

Aside from SOFCs, GDC has other uses:

As an oxygen sensor
In catalytic treatment of automobile exhaust fumes^{[citation needed]}

References

^ ^a ^b ^c Badwal, S. P. S.; Fini, D.; Ciacchi, F. T.; Munnings, C.; Kimpton, J. A.; Drennan, J. (2013). "Structural and microstructural stability of ceria – gadolinia electrolyte exposed to reducing environments of high temperature fuel cells". Journal of Materials Chemistry A. 1 (36): 10768. doi:10.1039/c3ta11752a.
^ "Gadolinia doped Ceria GDC | AMERICAN ELEMENTS ® Supplier & Info". Americanelements.com. 2010-08-24. Retrieved 2013-08-16.
^ "Publica". Publica.fraunhofer.de. Retrieved 2013-08-16.
^ Garche, Jurgen. et al., ed. Encyclopedia of Electrochemical Power Sources. Oxford: Newnes, 2009.
^ "Comparative Study for Average Crystallite Size of gadolinium doped-ceria synthesized by different methods" (PDF). Sbpmat.org.br. Retrieved 2013-08-16.
^ "Fabrication of 10%Gd-doped ceria (GDC)/NiO-GDC half cell for low or intermediate temperature solid oxide fuel cells using spray pyrolysis". Retrieved 2013-08-16.
^ Luo, Dan; Luo, Zhongyang; Yu, Chunjiang; Cen, Kefa (2007). "Study on Agglomeration and Densification Behaviors of Gadolinium-Doped Ceria Ceramics". Journal of Rare Earths. 25 (2): 163–167. doi:10.1016/S1002-0721(07)60066-0.
^ ^a ^b Rossinyol, Emma, et al. "Gadolinium Doped Ceria Nanocrystals Synthesized From Mesoporous Silica." J Nanopart Res (2008) 10:369–375 doi:10.1007/s11051-007-9257-z
^ Halmenschlager, C. M.; Neagu, R.; Rose, L.; Malfatti, C. F.; Bergmann, C. P. (2013-02-01). "Influence of the process parameters on the spray pyrolysis technique, on the synthesis of gadolinium doped-ceria thin film". Materials Research Bulletin. 48 (2): 207–213. doi:10.1016/j.materresbull.2012.09.073. ISSN 0025-5408.
^ Bocchetta, Patrizia; Santamaria, Monica; Di Quarto, Francesco (2012). "Electrodeposition of Supported Gadolinium-Doped Ceria Solid Solution Nanowires". Journal of the Electrochemical Society. 159 (5). Jes.ecsdl.org: E108–E114. doi:10.1149/2.005206jes.