169 results found
Harrington GF, Skinner SJ, Kilner JA, 2018, Can solute segregation in ceramic materials be reduced by lattice strain?, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Vol: 101, Pages: 1310-1322, ISSN: 0002-7820
Shih DPC, Aguadero A, Skinner SJ, 2018, Improvement of ionic conductivity in A-site lithium doped sodium bismuth titanate, Solid State Ionics, Vol: 317, Pages: 32-38, ISSN: 0167-2738
© 2018 Elsevier B.V. Oxide-ion conductors play a significant role in various applications such as solid oxide fuel cells (SOFCs), oxygen separation membranes and sensors. Recently, high ionic conductivity (~ 1 × 10 − 4 S cm − 1 at 600 °C) was found in sodium bismuth titanate (NBT), which originates from oxygen vacancies compensating the introduced Bi-deficiency. By providing pathways with low diffusion barriers, the highly polarizable Bi 3 + ions with 6s 2 lone pair electrons and weak Bi–O bonds are also beneficial for the migration of oxygen ions. Here we report the influence of lithium doping on the electrical properties of NBT. The optimal doping level of 4 at% Li on the Bi-site improves the ionic conductivity by one order of magnitude to ~ 7 × 10 − 3 S cm − 1 at 600 °C without changing the conduction mechanism, which could be attributed to an increase in the oxygen vacancy concentration based on an acceptor doping mechanism. A further increase in Li content does not improve the total conductivity. Oxygen diffusion data were acquired by the Isotope Exchange Depth Profile (IEDP) method in combination with Secondary Ion-Mass Spectrometry (SIMS). The oxygen self-diffusion coefficients (e.g. 7.04 × 10 − 9 cm 2 s − 1 at 600 °C) are in excellent agreement with the values derived from impedance spectroscopy data, suggesting that the oxygen ions are the main charge carriers in the system. Furthermore, a degradation test was performed for 100 h under a variety of atmospheres, showing only a slight decrease in conductivity in both air and oxygen atmospheres attributed to the loss of material from the A-site. Comparison with other oxide-ion conductors indicates that Li-doped NBT materials are promising candidates for intermediate temperature SOFC applications.
Harrington GF, Cavallaro A, McComb DW, et al., 2017, The effects of lattice strain, dislocations, and microstructure on the transport properties of YSZ films, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 19, Pages: 14319-14336, ISSN: 1463-9076
Lerdprom W, Li C, Jayaseelan DD, et al., 2017, Temperature dependence of electrical conductivity of a green porcelain mixture, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, Vol: 37, Pages: 343-349, ISSN: 0955-2219
Li C, Pramana SS, Ni N, et al., 2017, Surface Chemistry of La0.99Sr0.01NbO4-d and Its Implication for Proton Conduction, ACS APPLIED MATERIALS & INTERFACES, Vol: 9, Pages: 29633-29642, ISSN: 1944-8244
Pramana SS, Cavallaro A, Qi J, et al., 2017, Understanding surface structure and chemistry of single crystal lanthanum aluminate, SCIENTIFIC REPORTS, Vol: 7, ISSN: 2045-2322
Ravella UK, Liu J, Corbel G, et al., 2017, Cationic Interdiffusion at the SOFC Electrolyte/Cathode Interface in La 2 Mo 2 O 9 /La 0.8 Sr 0.2 MnO 3-δ, ChemistrySelect, Vol: 2, Pages: 5616-5623, ISSN: 2365-6549
Tonus F, Bahout M, Dorcet V, et al., 2017, A-site order-disorder in the NdBaMn<inf>2</inf>O<inf>5+δ</inf>SOFC electrode material monitored in situ by neutron diffraction under hydrogen flow, Journal of Materials Chemistry A, Vol: 5, Pages: 11078-11085, ISSN: 2050-7488
© 2017 The Royal Society of Chemistry. The A-site disordered perovskite manganite, Nd 0.5 Ba 0.5 MnO 3 , has been obtained by heating the A-site-ordered and vacancy ordered layered double perovskite, NdBaMn 2 O 5 , in air at 1300 °C for 5 h. Combined transmission electron microscopy (TEM) images and neutron powder diffraction (NPD) analysis at 25 °C revealed that Nd 0.5 Ba 0.5 MnO 3 has a pseudotetragonal unit cell with orthorhombic symmetry (space group Imma, √2a p × 2a p × √2a p ) at 20 °C with the cell dimensions a = 5.503(1) Å, b = 7.7962(4) Å, c = 5.502(1) Å, in contrast to Pm3m or Cmcm that have been previously stated from X-ray diffraction studies. The in situ neutron diffraction study carried out on Nd 0.5 Ba 0.5 MnO 3 in hydrogen flow up to T ∼ 900 °C, allows monitoring the A-site cation disorder-order structural phase transition of this representative member of potential SOFC anode materials between air sintering conditions and hydrogen working c onditions. Oxygen loss from Nd 0.5 Ba 0.5 MnO 3 proceeds with retention of A-site disorder until the oxygen content reaches the Nd 0.5 Ba 0.5 MnO 2.5 composition at 600 °C. The phase transition to layered NdBaMn 2 O 5 and localization of the oxygen vacancies in the Nd layer proceeds at 800 °C with retention of the oxygen content. Impedance spectroscopy measurements for the oxidized A-site ordered electrode material, NdBaMn 2 O 6 , screen printed on a Ce 0.9 Gd 0.1 O 2-δ (CGO) electrolyte showed promising electrochemical performance in air at 700 °C with a polarization resistance of 1.09 Ω cm 2 without any optimization.
Wu K-T, Tellez H, Druce J, et al., 2017, Surface chemistry and restructuring in thin-film Lan+1NinO3n+1 (n=1, 2 and 3) Ruddlesden-Popper oxides, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 5, Pages: 9003-9013, ISSN: 2050-7488
Inprasit T, Wongkasemjit S, Limthongkul P, et al., 2016, Synthesis and electrical property study of La3Ni2MO9 (M=Nb and TA), MATERIALS LETTERS, Vol: 162, Pages: 37-39, ISSN: 0167-577X
Ni N, Cooper SJ, Williams R, et al., 2016, Degradation of (La0.6Sr0.4)(0.95)(Co0.2Fe0.8)O3-delta Solid Oxide Fuel Cell Cathodes at the Nanometer Scale and below, ACS APPLIED MATERIALS & INTERFACES, Vol: 8, Pages: 17360-17370, ISSN: 1944-8244
Ni N, Skinner S, 2016, Combined Cr and Mo poisoning of (La,Sr)(Co,Fe)O-3 (-) (delta) solid oxide fuel cell cathodes at the nanoscale, SOLID STATE IONICS, Vol: 288, Pages: 28-31, ISSN: 0167-2738
Pramana SS, Baikie T, An T, et al., 2016, Correlation of Local Structure and Diffusion Pathways in the Modulated Anisotropic Oxide Ion Conductor CeNbO4.25, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 138, Pages: 1273-1279, ISSN: 0002-7863
Ravella UK, Liu J, Corbel G, et al., 2016, Cationic Intermixing and Reactivity at the La2Mo2O9/La0.8Sr0.2MnO3- Solid Oxide Fuel Cell Electrolyte-Cathode Interface, CHEMSUSCHEM, Vol: 9, Pages: 2182-2192, ISSN: 1864-5631
Skinner SJ, 2016, In situ diffraction approaches to characterisation of solid oxide fuel cell electrodes, Structural Characterization Techniques: Advances and Applications in Clean Energy, Pages: 59-74, ISBN: 9789814669351
© 2016 Pan Stanford Publishing Pte. Ltd. All rights reserved. Solid oxide fuel cells offer an excellent solution to current challenges in energy generation. The electrodes are the key functional components and understanding the phase evolution, reactivity and stability under operating conditions is essential if these devices are to be commercially viable products. Diffraction techniques are powerful tools that provide detailed characterisation of the materials central to device development. In-situ measurements are vital in mimicking the operating conditions of cells and in aiding our understanding of the key mechanisms of device degradation and reactivity. Several aspects of the use of in-situ techniques will be outlined in this chapter, focusing on powder diffraction techniques.
Tonus F, Bahout M, Dorcet V, et al., 2016, Redox behavior of the SOFC electrode candidate NdBaMn2O5+delta investigated by high-temperature in situ neutron diffraction: first characterisation in real time of an LnBaMn(2)O(5.5) intermediate phase, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 4, Pages: 11635-11647, ISSN: 2050-7488
Tonus F, Skinner SJ, 2016, In-situ neutron diffraction study of cathode/electrolyte interactions under electrical load and elevated temperature, Solid State Sciences, Vol: 55, Pages: 88-92, ISSN: 1293-2558
© 2016 The Authors. Fuel cells are proposed as a future energy conversion technology that will reduce greenhouse gas emissions at the point of operation due to their ability to produce electrical energy from non-hydrocarbon fuel sources. The Solid Oxide Fuel Cell (SOFC) is amongst the most efficient fuel cell types, however, due to the high cell operating temperature cation diffusion occurs between the different components of the cell, resulting in rapid degradation of the power output. In this paper we investigate cation migration between the promising intermediate temperature-SOFC cathode La 1-xSr xCo 1-yFe y O 3-δ (LSCF) and a fluorite type electrolyte Ce 1-xPr xO 2-δ (CPO). The crystallographic structure evolution and degradation of the materials were studied by neutron diffraction in-situ under pseudo-operating conditions, i.e. at 600 °C under air and under electrical polarisation. The lattice parameter and cation occupancy evolution were analysed by Rietveld refinement as a function of time and applied potential. The materials were found to be stable, as no impurity formation, lattice parameter or site occupancy evolution was observed during the experiment. However La migration prior to the experiment from LSCF to CPO was observed as well as B-site vacancies in LSCF.
Wachowski S, Mielewczyk-Gryn A, Zagorski K, et al., 2016, Influence of Sb-substitution on ionic transport in lanthanum orthoniobates, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 4, Pages: 11696-11707, ISSN: 2050-7488
Yanez-Gonzalez A, Ruiz-Trejo E, van Wachem B, et al., 2016, Developmet of an optical thermal history coating sensor based on the oxidation of a divalent rare earth ion phosphor, MEASUREMENT SCIENCE AND TECHNOLOGY, Vol: 27, ISSN: 0957-0233
Yanez-Gonzalez A, van Wachem B, Skinner S, et al., 2016, On the kinetics of thermal oxidation of the thermographic phosphor BaMgAL(10)O(17):Eu, MATERIALS & DESIGN, Vol: 108, Pages: 145-150, ISSN: 0264-1275
Bahout M, Pramana SS, Hanlon JM, et al., 2015, Stability of NdBaCo2−xMnxO5+δ (x = 0, 0.5) layered perovskites under humid conditions investigated by high-temperature in situ neutron powder diffraction, Journal of Materials Chemistry A, Vol: 3, Pages: 15420-15431, ISSN: 2050-7496
The double perovskites NdBaCo2−xMnxO5+δ (x = 0 and 0.5) were investigated using in situ high temperature neutron powder diffraction in dry argon and wet atmospheres (40% D2O/argon and 40% D2O/air) in order to assess their stability as cathodes in proton conducting fuel cells. The x = 0 oxide loses oxygen on heating in dry argon at T > 400 °C and exhibits an oxygen vacancy order–disorder transition as evidenced by the orthorhombic Pmmm to tetragonal P4/mmm transition. Refinement of site occupancy factors suggests that the oxygen vacancies mainly form in the Nd layers and to a lesser extent at the equatorial positions of the transition metal polyhedra; at 800 °C, δ ∼ 0. When the gas was changed to wet argon at 800 °C and the sample cooled to 260 °C, no structural modification or change in the oxygen content was detected and no impurity phases formed, highlighting the excellent stability of the sample in wet atmospheres. On switching the gas to wet air at 260 °C, thermal analysis and neutron powder diffraction data together reveal that the sample intercalates mainly oxygen rather than proton defects within a two-phase process involving two orthorhombic phases, reflecting the symmetry of the reduced and oxidised materials. On heating, the sample transforms at T ≥ 600 °C to a single tetragonal phase whose symmetry is retained up to 800 °C and on subsequent cooling. The x = 0.5 material prepared in argon adopted a tetragonal P4/mmm structure at RT with δ ∼ 0. Its symmetry remains tetragonal on heating/cooling in wet argon. On changing the gas to wet air at 260 °C, it takes up oxygen via a two-phase process involving two tetragonal phases. Since fast oxidation is the main process that fills the oxygen vacancies of these double perovskites in wet air, a large oxygen deficiency seems to be not the only requirement for effective proton incorporation in this family of materials with basic characteristi
Bahout M, Pramana SS, Hanlon JM, et al., 2015, Stability of NdBaCo2-xMnxO5+delta (x=0, 0.5) layered perovskites under humid conditions investigated by high-temperature in situ neutron powder diffraction, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 3, Pages: 15420-15431, ISSN: 2050-7488
Feist JP, Nicholls JR, Fraser MJ, et al., 2015, Luminescent Material Compositions and structures incorporating the same, US9045830
Gonzalez AY, Skinner S, Beyrau F, et al., 2015, Reusable Thermal History Sensing via Oxidation of a Divalent Rare Earth Ion-Based Phosphor Synthesized by the Sol-Gel Process, HEAT TRANSFER ENGINEERING, Vol: 36, Pages: 1275-1281, ISSN: 0145-7632
Inprasit T, Wongkasemjit S, Skinner SJ, et al., 2015, Effect of Sr substituted La2-xSrxNiO4+delta (x=0, 0.2, 0.4, 0.6, and 0.8) on oxygen stoichiometry and oxygen transport properties, RSC ADVANCES, Vol: 5, Pages: 2486-2492, ISSN: 2046-2069
Niania MA, Podor R, Skinner SJ, et al., 2015, In-situ surface analysis of SOFC cathode degradation using high temperature environmental scanning electron microscopy, Pages: 665-670, ISSN: 1938-5862
© The Electrochemical Society. In this study the surface properties of LSCF have been studied in-situ from room temperature to 1000°C using a High Temperature Environmental Scanning Electron Microscope (HT-ESEM) under a number of different atmospheres. Dense, polished La < inf > 0.6 < /inf > Sr < inf > 0.4 < /inf > Co < inf > 0.2 < /inf > Fe < inf > 0.8 < /inf > O < inf > 3-δ < /inf > (LSCF) was observed during thermal annealing under vacuum, pure oxygen, pure water and humid air atmospheres. The effect each atmosphere had on the surface morphology has been characterized in real time and analysed chemically using EDX. Significant differences in the surface behaviour were seen under each atmosphere. The results observed in the HT-ESEM were complementary to surface exchange measurements performed in air and have enabled a more detailed understanding of SOFC cathode decomposition.
Regoutz A, Egdell RG, Morgan DJ, et al., 2015, Electronic and surface properties of Ga-doped In2O3 ceramics, APPLIED SURFACE SCIENCE, Vol: 349, Pages: 970-982, ISSN: 0169-4332
Wu J, Pramana SS, Skinner SJ, et al., 2015, Why Ni is absent from the surface of La2NiO4+delta?, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 3, Pages: 23760-23767, ISSN: 2050-7488
Wu KT, Téllez H, Druce J, et al., 2015, Surface composition of layered Ruddlesden-Popper La<inf>n+1</inf>Ni<inf>n</inf>O3<inf>n+1</inf> (n = 1, 2 and 3) epitaxial films, Pages: 89-93, ISSN: 1938-5862
© The Electrochemical Society. Layered Ruddlesden-Popper (RP) type oxides, formulated La < inf > n+1 < /inf > Ni < inf > n < /inf > O < inf > 3n+1 < /inf > (n = 1, 2 and 3), have recently been suggested as candidates for IT-SOFC cathodes. The oxygen surface exchange activity is strongly influenced by the surface composition and atomic surface structure where the adsorption and dissociation of molecular oxygen take place. It is therefore necessary to understand the surface and near-surface chemical compositions of the cathode materials. In this work, the surface and near-surface composition of epitaxial films in the RP series was systematically investigated using low-energy ion scattering (LEIS).
Yanez-Gonzalez A, Ruiz-Trejo E, van Wachem B, et al., 2015, A detailed characterization of BaMgAl10O17:Eu phosphor as a thermal history sensor for harsh environments, SENSORS AND ACTUATORS A-PHYSICAL, Vol: 234, Pages: 339-345, ISSN: 0924-4247
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