Mixed conductivity, structural and microstructural characterization of titania-doped yttria tetragonal zirconia polycrystalline/titania-doped yttria stabilized zirconia composite anode matrices

Journal Article · Tue Feb 15 00:00:00 EST 2011 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2010.12.006· OSTI ID:21494208

Maczka, M ^[1]

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1. Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, Wroclaw 2 (Poland)

Taking advantage of the fact that TiO{sub 2} additions to 8YSZ cause not only the formation of a titania-doped YSZ solid solution but also a titania-doped YTZP solid solution, composite materials based on both solutions were prepared by solid state reaction. In particular, additions of 15 mol% of TiO{sub 2} give rise to composite materials constituted by 0.51 mol fraction titania-doped yttria tetragonal zirconia polycrystalline and 0.49 mol fraction titania-doped yttria stabilized zirconia (0.51TiYTZP/0.49TiYSZ). Furthermore, Y{sub 2}(Ti{sub 1-y}Zr{sub y}){sub 2}O{sub 7} pyrochlore is present as an impurity phase with y close to 1, according to FT-Raman results. Lower and higher additions of titania than that of 15 mol%, i.e., x=0, 5, 10, 20, 25 and 30 mol% were considered to study the evolution of 8YSZ phase as a function of the TiO{sub 2} content. Furthermore, zirconium titanate phase (ZrTiO{sub 4}) is detected when the titania content is equal or higher than 20 mol% and this phase admits Y{sub 2}O{sub 3} in solid solution according to FE-SEM-EDX. The 0.51TiYTZP/0.49TiYSZ duplex material was selected in this study to establish the mechanism of its electronic conduction under low oxygen partial pressures. In the pO{sub 2} range from 0.21 to 10{sup -7.5} atm. the conductivity is predominantly ionic and constant over the range and its value is 0.01 S/cm. The ionic plus electronic conductivity is 0.02 S/cm at 1000 {sup o}C and 10{sup -12.3} atm. Furthermore, the onset of electronic conductivity under reducing conditions exhibits a -1/4 pO{sub 2} dependence. Therefore, it is concluded that the n-type electronic conduction in the duplex material can be due to a small polaron-hopping between Ti{sup 3+} and Ti{sup 4+}. -- Graphical abstract: FE-SEM micrograph of a polished and thermal etched surface of a Ti-doped YTZP/Ti-doped YSZ composite material. Display Omitted Research highlights: {yields} Ti-doped YTZP/Ti-doped YSZ composite materials are mixed conductors under low partial pressures. {yields} From 5 mol% of TiO{sub 2}, Y{sub 2}(Ti{sub 1-y},Zr{sub y}){sub 2}O{sub 7} pyrochlore is present as a minor phase, being y close to 1 according to FT-Raman studies. {yields} The onset of the electronic conductivity under reducing conditions exhibit a -1/4 pO{sub 2} dependence. The n-type electronic conduction is due to a small polaron-hopping between Ti{sup 3+} and Ti{sup 4+}.

• OSTI ID: 21494208
• Journal Information: Journal of Solid State Chemistry, Vol. 184, Issue 2; Other Information: DOI: 10.1016/j.jssc.2010.12.006; PII: S0022-4596(10)00544-X; Copyright (c) 2010 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COMPOSITE MATERIALS
DOPED MATERIALS
MICROSTRUCTURE
OXYGEN
PARTIAL PRESSURE
POLYCRYSTALS
PYROCHLORE
SCANNING ELECTRON MICROSCOPY
SOLID OXIDE FUEL CELLS
SOLID SOLUTIONS
SURFACES
TITANATES
TITANIUM IONS
TITANIUM OXIDES
YTTRIUM OXIDES
ZIRCONIUM OXIDES
CHALCOGENIDES
CHARGED PARTICLES
CRYSTALS
DIRECT ENERGY CONVERTERS
DISPERSIONS
ELECTROCHEMICAL CELLS
ELECTRON MICROSCOPY
ELEMENTS
FUEL CELLS
HIGH-TEMPERATURE FUEL CELLS
HOMOGENEOUS MIXTURES
IONS
MATERIALS
MICROSCOPY
MINERALS
MIXTURES
NONMETALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SOLID ELECTROLYTE FUEL CELLS
SOLUTIONS
THERMODYNAMIC PROPERTIES
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
ZIRCONIUM COMPOUNDS