Conductivity studies of dense yttrium-doped BaZrO{sub 3} sintered at 1325 deg. C

Journal Article · Sat Dec 15 04:00:00 EST 2007 · Journal of Solid State Chemistry

OSTI ID:21043779

Shanwen, Tao ^[1]

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1. School of Chemistry, University of Saint Andrews, Saint Andrews, Fife KY16 9ST (United Kingdom)

High-temperature proton conductors have wide applications in the areas of fuel cells, electrolysis and hydrogen separation. Barium zirconate-based materials are of interest due to their good stability and high protonic conductivity. The reported conductivity of these ceramic materials is generally less than 10{sup -2} S/cm, even at high temperatures. This is not high enough for an electrolyte-supported device to achieve an ASR of less than 0.2 {omega} cm{sup 2} therefore thin film electrolytes are required for successful application. As BaZrO{sub 3}-based materials have to be sintered at temperatures as high as 1700 deg. C, this makes it difficult to find a suitable supporting electrode which will not undergo significant chemical reaction with the BaZrO{sub 3}-based electrolyte during fabrication of the required electrode supported electrolyte. In this paper, proton-conducting BaZr{sub 0.8}Y{sub 0.2}O{sub 2.9} was successfully sintered at 1325 deg. C with a relative density of 96% via addition of 1 wt% ZnO. Fabrication of electrochemical cells using proton-conducting BaZr{sub 0.8}Y{sub 0.2}O{sub 2.9} as the electrolyte thus becomes possible. The formula of the 1 wt% ZnO added sample is Ba{sub 0.97}Zr{sub 0.77}Y{sub 0.19}Zn{sub 0.04}O{sub 3-{delta}} which exhibits a tetragonal structure with space group P4/mbm (127); a=5.9787(1) A, c=4.2345(1) A, V=151.36(1) A{sup 3}. It was found that a solid solution was formed for a limited range of Zn doping. Conductivity has been studied as a function of atmosphere (air, dry and wet 5% H{sub 2}/Ar) with the changes in bulk and grain boundary on changing atmosphere being monitored as a function of time. The total conductivity of Ba{sub 0.97}Zr{sub 0.77}Y{sub 0.19}Zn{sub 0.04}O{sub 3-{delta}} is 1.0x10{sup -3} S/cm above 600 deg. C therefore it may be used as a proton-conducting thin film electrolyte for efficient electrochemical devices at such temperatures. The grain boundary resistance is insignificant at high temperature for the well-sintered sample. - Graphical abstract: Total conductivity of BaZr{sub 0.8}Y{sub 0.2}O{sub 3-{delta}} samples in wet 5% H{sub 2}/Ar with (red) and without (green) addition of 1 wt% ZnO.

• OSTI ID: 21043779
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 12 Vol. 180; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
BARIUM COMPOUNDS
CHEMICAL REACTIONS
DOPED MATERIALS
ELECTROCHEMISTRY
ELECTRODES
ELECTROLYSIS
ELECTROLYTES
FUEL CELLS
GRAIN BOUNDARIES
HYDROGEN
PROTONS
SINTERING
SOLID SOLUTIONS
SPACE GROUPS
TEMPERATURE RANGE 1000-4000 K
TETRAGONAL LATTICES
THIN FILMS
YTTRIUM COMPOUNDS
ZINC OXIDES
ZIRCONATES