Browsing by Author "Lincoln, FJ"

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    New quenched-in fluorite-type materials in the Bi2O3-La2O3-PbO system: synthesis and complex phase behaviour up to 750 degrees C
    (Pergamon-Elsevier Science Ltd, 2011-04-01) Webster, NAS; Hartlieb, KJ; Saines, PJ; Ling, CD; Lincoln, FJ
    New quenched-in fluorite-type materials with composition (BiO1.5)(0.94-x)(LaO1.5)(0.06)(PbO)(x), x = 0.02, 0.03, 0.04 and 0.05, were synthesised by solid state reaction. The new materials undergo a number of phase transformations during heating between room temperature and 750 degrees C, as indicated by differential thermal analysis. Variable temperature X-ray diffraction performed on the material (BiO1.5)(0.92)(LaO1.5)(0.06)(PbO)(0.02) revealed that the quenched-in fcc fluorite-type material first undergoes a transformation to a beta-Bi2O3-type tetragonal phase around 400 degrees C. In the range 450-700 degrees C, alpha-Bi2O3-type monoclinic, Bi12PbO19-type bcc and beta(1)/beta(2)-type rhombohedral phases, and what appeared to be a epsilon-type monoclinic phase, were observed, before a single-phase fluorite-type material was regained at 750 degrees C. (C) 2010 Elsevier Ltd.
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    Structural and conductivity evolution of fluorite-type Bi2O3-Er2O3-PbO solid electrolytes during long-term annealing
    (Elsevier, 2008-08) Webster, NAS; Ling, CD; Raston, CL; Lincoln, FJ
    Quenched-in fcc fluorite-type materials in the Bi2O3-Er2O3-PbO system were annealed in air at 500 and 600 degrees C for up to 2000 h. Each material experienced a conductivity-lowering structural transformation, thus making them unsuitable for use in SOFCs. For example, the materials (BiO1.5)(0.80)(ErO1.5)(0.20-x)(PbO)(x), x = 0.03, 0.06 and 0.09, underwent a fluorite-type to tetragonal transformation during annealing at 500 degrees C due to (100) oxide-ion vacancy ordering, and the rate of conductivity decay at 500 degrees C increased with increasing Pb2+/Er3+ ratio. © 2008, Elsevier Ltd.
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    Structure and conductivity of new fluorite-type Bi2O3-Er2O3-PbO materials
    (Elsevier, 2007-10) Webster, NAS; Ling, CD; Raston, CL; Lincoln, FJ
    Fluorite-type fcc phases have been synthesised in the system Bi2O3-Er2O3-PbO by solid state reaction, and a partial air-quenchable domain of the fluorite-type phase has been established. Some of these materials display high oxide ion conductivities, notably (BiO1.5)(0.80)(ErO1.5)(0.11)(PbO)(0 09) and (BiO1.5)(0.85)(ErO1.5)(0.12)(PbO)(0.03), which have conductivities of 0.49 and 0.72 S cm(-1) at 750 degrees C, respectively, placing them among the most conductive Bi2O3-based materials. Conductivity was found to increase with increasing Pb2+/Er3+ ratio and decreasing (Er3+ + Pb2+)/Bi3+ ratio. Positional disorder in the oxide ion sublattice was characterised by neutron powder diffraction. At room temperature, the oxide ion sublattice appeared to be completely disordered, with oxide ions only in 32f and 48i sites, and changes in occupancy with increasing Pb2+/Er3+ and (Er3+ + Pb2+)/Bi3+ ratios were not significant. At 700 degrees C, there appeared to be oxide ions in 8c sites for the material (BiO1.5)(0.80)(ErO1.5)(0.11)(PbO)(0 09), with a correspondingly smaller occupancy of the 32f sites, whilst the occupancy of the 48i sites had not changed significantly. © 2007, Elsevier Ltd.