B-site substitutions in LaNb{sub 1-x}M{sub x}O{sub 4-{delta}} materials in the search for potential proton conductors (M=Ga, Ge, Si, B, Ti, Zr, P, Al)

Journal Article · Fri Apr 15 04:00:00 EDT 2011 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2011.02.012· OSTI ID:21494250

Brandao, A D ^[1]; Gracio, J ^[2]; Mather, G C ^[3]; Kharton, V V ^[1]

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1. Dept. Ceramics and Glass Engineering, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal)
2. Nanotechnology Research Division, Centre of Mechanical Technology and Automation, University of Aveiro, 3810 193 Aveiro (Portugal)
3. Institute of Ceramics and Glass, CSIC, Cantoblanco, 28049 Madrid (Spain)

The solid solubilities of potential B-site dopants in LaNb{sub 1-x}M{sub x}O{sub 4-{delta},} materials, M=Ga, Ge, Si, Al, B, P, Zr or Ti, have been investigated in the search for possible novel proton conductors. In general, the solubility levels of these cations were found to be very low (x{<=}0.03). At the maximum value x=0.03, only compositions containing Ti, Ge, Ga and Si appeared pure at the limit of resolution of XRD. The literature phase diagram, La{sub 2}O{sub 3}-Nb{sub 2}O{sub 5}-ZrO{sub 2}, has been re-analysed for compositions of low Zr-content around the composition LaNbO{sub 4}. The electrical properties of phase pure Ti-doped compositions have been studied. Higher bulk and total conductivities were observed in wet than dry conditions, suggesting a significant protonic contribution to total conductivity. In wet conditions, the activation energy for bulk conductivity of LaNb{sub 0.98}Ti{sub 0.02}O{sub 4-{delta}} was found to be much higher than that of an A-site, Sr-doped material, Sr{sub 0.02}La{sub 0.98}NbO{sub 4-{delta},} of similar acceptor dopant concentration. The Sr-doped composition offered higher conductivities than the Ti-doped composition up to approximately 900{sup o}C. -- Graphical abstract: Comparison of total (open symbols) and bulk (closed symbols) conductivities measured in wet (p(H{sub 2}O){approx}0.026 atm.) nitrogen and oxygen atmospheres for LaNb{sub 0.98}Ti{sub 0.02}O{sub 4-{delta}} (LNT2O) and Sr{sub 0.02}La{sub 0.98}NbO{sub 4-{delta}} (S2LNO) materials. Display Omitted Research highlights: {yields} The article investigates solid solubilities of potential B-site dopants in the potential proton conductor LaNb{sub 1-x}M{sub x}O{sub 4-{delta},} {yields} The literature phase diagram, La{sub 2}O{sub 3}-Nb{sub 2}O{sub 5}-ZrO{sub 2}, has been corrected for compositions of low Zr-content around the composition LaNbO{sub 4}. {yields} The electrical properties of Ti-doped compositions have been assessed in wet and dry conditions. {yields} Comparison has been made between the electrical properties of B-site, Ti-doped, compositions and A-site, Sr-doped, compositions.

• OSTI ID: 21494250
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 4 Vol. 184; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

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36 MATERIALS SCIENCE
ACTIVATION ENERGY
BARYONS
CATIONS
CERAMICS
CHALCOGENIDES
CHARGED PARTICLES
COHERENT SCATTERING
DIAGRAMS
DIFFRACTION
DIRECT ENERGY CONVERTERS
DOPED MATERIALS
ELECTRICAL PROPERTIES
ELECTROCHEMICAL CELLS
ELEMENTARY PARTICLES
ELEMENTS
ENERGY
FERMIONS
FUEL CELLS
HADRONS
HIGH-TEMPERATURE FUEL CELLS
INFORMATION
IONS
LANTHANUM COMPOUNDS
LANTHANUM NITRIDES
LANTHANUM OXIDES
MATERIALS
NIOBATES
NIOBIUM COMPOUNDS
NIOBIUM OXIDES
NITRIDES
NITROGEN
NITROGEN COMPOUNDS
NONMETALS
NUCLEONS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PHASE DIAGRAMS
PHYSICAL PROPERTIES
PNICTIDES
PROTONS
RARE EARTH COMPOUNDS
REFRACTORY METAL COMPOUNDS
SCATTERING
SOLID ELECTROLYTE FUEL CELLS
SOLID OXIDE FUEL CELLS
SOLUBILITY
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES