Publications
547 results found
Saranya AM, Pla D, Morata A, et al., 2015, Engineering Mixed Ionic Electronic Conduction in La0.8Sr0.2MnO3+δ Nanostructures through Fast Grain Boundary Oxygen Diffusivity, Advanced Energy Materials, ISSN: 1614-6840
Jalem R, Rushton MJD, Manalastas W, et al., 2015, Effects of Gallium Doping in Garnet-Type Li7La3Zr2O12 Solid Electrolytes, Chemistry of Materials, Vol: 27, Pages: 2821-2831, ISSN: 1520-5002
Garnet-type Li7La3Zr2O12 (LLZrO) is a candidate solid electrolyte material that is now being intensively optimized for application in commercially competitive solid state Li+ ion batteries. In this study we investigate, by force-field-based simulations, the effects of Ga3+ doping in LLZrO. We confirm the stabilizing effect of Ga3+ on the cubic phase. We also determine that Ga3+ addition does not lead to any appreciable structural distortion. Li site connectivity is not significantly deteriorated by the Ga3+ addition (>90% connectivity retained up to x = 0.30 in Li7–3xGaxLa3Zr2O12). Interestingly, two compositional regions are predicted for bulk Li+ ion conductivity in the cubic phase: (i) a decreasing trend for 0 ≤ x ≤ 0.10 and (ii) a relatively flat trend for 0.10 < x ≤ 0.30. This conductivity behavior is explained by combining analyses using percolation theory, van Hove space time correlation, the radial distribution function, and trajectory density.
Aguesse F, Roddatis V, Roqueta J, et al., 2015, Microstructure and ionic conductivity of LLTO thin films: Influence of different substrates and excess lithium in the target, SOLID STATE IONICS, Vol: 272, Pages: 1-8, ISSN: 0167-2738
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- Citations: 33
Tellez H, Druce J, Hong J-E, et al., 2015, Accurate and Precise Measurement of Oxygen Isotopic Fractions and Diffusion Profiles by Selective Attenuation of Secondary Ions (SASI), ANALYTICAL CHEMISTRY, Vol: 87, Pages: 2907-2915, ISSN: 0003-2700
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- Citations: 8
Ishihara T, Xie J, Shin TH, et al., 2015, Bi doped Pr<sub>6</sub>O<sub>11</sub> as fluorite oxide cathode for all-fluorite solid oxide fuel cells, JOURNAL OF POWER SOURCES, Vol: 275, Pages: 167-174, ISSN: 0378-7753
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- Citations: 10
Pergolesi D, Roddatis V, Fabbri E, et al., 2015, Probing the bulk ionic conductivity by thin film hetero-epitaxial engineering, SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS, Vol: 16, ISSN: 1468-6996
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- Citations: 16
Li M, Zhang H, Cook SN, et al., 2015, Dramatic Influence of A-Site Nonstoichiometry on the Electrical Conductivity and Conduction Mechanisms in the Perovskite Oxide Na<sub>0.5</sub>Bi<sub>0.5</sub>TiO<sub>3</sub>, CHEMISTRY OF MATERIALS, Vol: 27, Pages: 629-634, ISSN: 0897-4756
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- Citations: 183
Cooper SJ, Li T, Bradley RS, et al., 2015, Multi length-scale quantification of hierarchical microstructure in designed microtubular SOFC electrodes, Pages: 1857-1864, ISSN: 1938-5862
The transport properties of a micro-tubular solid oxide fuel cell (MT-SOFC) anode have been analysed by imaging and simulation at multiple length-scales. The anode support investigated was manufactured using a phase inversion-assisted co-extrusion process, which generated a hierarchical and highly anisotropic microstructure. The resulting pore network was observed to contain two distinct, but interacting transport systems. The features in these systems spanned several orders of magnitude and as such it was not possible to image or model them simultaneously. The simulations indicated that the design of the microstructure was beneficial for the radial transport required by these cells; however this conclusion was only obtained by considering diffusive systems at many length-scales.
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: 1938-6737
Layered Ruddlesden-Popper (RP) type oxides, formulated Lan+1NinO3n+1 (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).
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- Citations: 5
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
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.
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- Citations: 12
Kilner JA, Druce J, Ishihara T, 2015, Electrolytes, High-Temperature Solid Oxide Fuel Cells for the 21st Century: Fundamentals, Design and Applications, Pages: 85-132, ISBN: 9780124104839
This chapter discusses fundamental and practical aspects of electrolyte materials for solid oxide fuel cells (SOFCs). We focus on two main families of ceramic electrolytes; those with the fluorite crystal structure (ZrO2- and CeO2-based) and those with perovskite-related structures (La1 - x Sr x Ga1 - y Mg y O3 -(x+ y)/2, CaTiO3 and Brownmillerite). Fundamental factors influencing the oxide ionic conductivity are discussed, including the crystal structure, along with strategies to improve the conductivity by substitution with aliovalent cations to introduce extrinsic point defects (oxygen vacancies). Protonic conductivity in perovskite-structured ceramics is also discussed. Finally, we consider some of the alternative materials, including apatite-structured silicates and LAMOX. Although the latter two families are interesting, we highlight some of the challenges to be overcome for their implementation in practical SOFC systems.
Druce J, Téllez H, Ishihara T, et al., 2015, Surface composition and oxygen transport properties of LSCF: From bulk ceramics to devices, ECS Transactions, Vol: 68, Pages: 557-567, ISSN: 1938-5862
Although the oxygen surface exchange reactions are of utmost importance for Solid Oxide Fuel Cells and Solid Oxide Electrolyser operation and performance, their specific mechanisms are rather poorly understood. One part of the puzzle is to determine the composition of the surfaces and interfaces participating in the reactions. Ion beam techniques constitute powerful probes of the surface composition, as well as the oxygen transport properties. Here, we use the well-known mixed conducting perovskite LSCF to illustrate how ion beam techniques, such as secondary ion mass spectrometry (SIMS) and low energy ion scattering (LEIS), can be used to study fundamental material properties (e.g. oxygen tracer diffusion and atomic rearrangements), as well as segregation and impurity migration processes in model electrode structures.
Tarancón A, Morata A, Pla D, et al., 2015, Grain boundary engineering to improve ionic conduction in thin films for micro-SOFCs, ECS Transactions, Vol: 69, Pages: 11-16, ISSN: 1938-6737
New emerging disciplines are specifically devoted to study trivial and non-trivial effects resulting from working in the nanoscale, however, the implementation of these nanostructures in real devices is still a major challenge. Thin film deposition and silicon microtechnology is probably the most promising and straightforward combination for the reliable integration of nanomaterials in real devices. In particular, the implementation of pure ionic and mixed ionic/electronic conductors (MIECs) in thin film form allows the miniaturization of multiple solid state devices such as solid oxide fuel cells (SOFCs). In this work, we will present the implementation of novel nanoionics concepts in micro-SOFCs by using micro and nanofabrication technologies. We will put special attention on the contribution of grain boundaries to the mass transport properties in interface-dominated materials such as thin films. Grain boundary engineering will be presented as a powerful tool for reducing the resistance associated to electrolytes and even control the intrinsic transport nature and performance of MIEC materials.
Téllez H, Druce J, Shi Y, et al., 2015, Surface segregation and inter-diffusion of cations and impurities in microelectrodes for solid oxide fuel cells and electrolysers, ECS Transactions, Vol: 66, Pages: 69-77, ISSN: 1938-5862
The surface segregation and inter-diffusion of cations and impurities in La<inf>0.6</inf>Sr<inf>0.4</inf>Co<inf>0.8</inf>Fe<inf>0.2</inf>O<inf>3-δ</inf> (LSCF) electrode structures micro-patterned on a Zr<inf>0.84</inf>Y<inf>0.16</inf>O<inf>1.92</inf> (YSZ) single crystal was investigated by high-resolution Time-of-Flight Secondary Ion Mass Spectrometry and Low-Energy Ion Scattering. The outermost and near surface of the microelectrodes showed significant changes after patterning and electrochemical testing of the cell. As occurring in bulk LSCF ceramics, Sr segregation towards the surface is observed after annealing at 500°C. Furthermore, the electrode showed that impurities (i.e. Na, Si and Ca) originating from the YSZ electrolyte bulk migrate actively to the LSCF electrode during electrochemical testing. The impurity migration has implications for oxygen surface exchange at the cathodeelectrolyte and air interface for solid oxide fuel cells: the electrolyte YSZ surface becomes cleaner whereas the segregation of Sr to the LSCF outer surface seems to be suppressed with respect to the operation time of the device.
Druce J, Téllez H, Ishihara HT, et al., 2015, Surface segregation in solid oxide electrode materials occurring at intermediate temperatures, ECS Transactions, Vol: 66, Pages: 61-68, ISSN: 1938-5862
The segregation of constituent elements and impurities affects the surface composition of solid oxide electrode materials, and hence, the rate of the surface exchange reaction. In this work, we compare segregation occurring at 400 °C in Pr0.5Sr0.5CoO3-d (PSCO) and PrBaCo2O5-d (PBCO). The surface composition changes rapidly on annealing at low temperature, with segregation of the divalent cation evident after just 15 minutes. The PBCO contained a Na impurity which undergoes similar segregation behavior to the Ba, becoming the dominant surface cation after 2 hours of annealing. Although cation mobility in these materials is slow compared to oxygen, it is sufficient to cause significant changes in surface composition on timescales of the order of hours.
Jay EE, Rushton MJD, Chroneos A, et al., 2015, Genetics of superionic conductivity in lithium lanthanum titanates, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 17, Pages: 178-183, ISSN: 1463-9076
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- Citations: 79
Druce J, Tellez H, Ishihara T, et al., 2015, Oxygen exchange and transport in dual phase ceramic composite electrodes, FARADAY DISCUSSIONS, Vol: 182, Pages: 271-288, ISSN: 1359-6640
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- Citations: 27
Tellez H, Druce J, Kilner JA, et al., 2015, Relating surface chemistry and oxygen surface exchange in LnBaCo<sub>2</sub>O<sub>5+δ</sub> air electrodes, FARADAY DISCUSSIONS, Vol: 182, Pages: 145-157, ISSN: 1359-6640
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- Citations: 32
Rupp GM, Tellez H, Druce J, et al., 2015, Surface chemistry of La<sub>0.6</sub>Sr<sub>0.4</sub>CoO<sub>3-δ</sub> thin films and its impact on the oxygen surface exchange resistance, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 3, Pages: 22759-22769, ISSN: 2050-7488
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- Citations: 99
Tellez H, Druce J, Ju Y-W, et al., 2014, Surface chemistry evolution in LnBaCo<sub>2</sub>O<sub>5+δ</sub> double perovskites for oxygen electrodes, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, Vol: 39, Pages: 20856-20863, ISSN: 0360-3199
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- Citations: 51
Druce J, Tellez H, Simrick N, et al., 2014, Surface composition of solid oxide electrode structures by laterally resolved low energy ion scattering (LEIS), INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, Vol: 39, Pages: 20850-20855, ISSN: 0360-3199
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- Citations: 10
Taub S, Williams REA, Wang X, et al., 2014, The effects of transition metal oxide doping on the sintering of cerium gadolinium oxide, ACTA MATERIALIA, Vol: 81, Pages: 128-140, ISSN: 1359-6454
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- Citations: 24
Bayliss RD, Cook SN, Kotsantonis S, et al., 2014, Oxygen Ion Diffusion and Surface Exchange Properties of the α- and δ-phases of Bi<sub>2</sub>O<sub>3</sub> (vol 4, 1301575, 2014), ADVANCED ENERGY MATERIALS, Vol: 4, ISSN: 1614-6832
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- Citations: 1
Bayliss RD, Cook SN, Scanlon DO, et al., 2014, Understanding the defect chemistry of alkali metal strontium silicate solid solutions: insights from experiment and theory, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 2, Pages: 17919-17924, ISSN: 2050-7488
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- Citations: 31
Druce J, Tellez H, Burriel M, et al., 2014, Surface termination and subsurface restructuring of perovskite-based solid oxide electrode materials, Energy and Environmental Science, Vol: 7, Pages: 3593-3599, ISSN: 1754-5692
We study the outer atomic surfaces of a series of perovskite-based ceramics using low energy ion scattering spectroscopy. After high temperature treatment, segregated A-site (or acceptor substituent) cations dominate the outer surfaces with no B-site cations detected. We also find evidence of an associated B-cation enriched region below the surface.
Berenov A, Atkinson A, Kilner J, et al., 2014, Oxygen tracer diffusion and surface exchange kinetics in Ba0.5Sr0.5Co0.8Fe0.2O3-delta, Solid State Ionics, Vol: 268, Pages: 102-109, ISSN: 1872-7689
Aguesse F, Lopez del Amo JM, Roddatis V, et al., 2014, Enhancement of the Grain Boundary Conductivity in Ceramic Li<sub>0.34</sub>La<sub>0.55</sub>TiO<sub>3</sub> Electrolytes in a Moisture-Free Processing Environment, ADVANCED MATERIALS INTERFACES, Vol: 1, ISSN: 2196-7350
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- Citations: 33
Slodczyk A, Sharp MD, Upasen S, et al., 2014, Combined bulk and surface analysis of the BaCe<sub>0.5</sub>Zr<sub>0.3</sub>Y<sub>0.16</sub>Zn<sub>0.04</sub>O<sub>3-</sub> <sub>δ</sub> (BCZYZ) ceramic proton-conducting electrolyte, 19th International Conference on Solid State Ionics (SSI), Publisher: ELSEVIER SCIENCE BV, Pages: 870-874, ISSN: 0167-2738
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- Citations: 34
Druce J, Ishihara T, Kilner J, 2014, Surface composition of perovskite-type materials studied by Low Energy Ion Scattering (LEIS), 19th International Conference on Solid State Ionics (SSI), Publisher: ELSEVIER, Pages: 893-896, ISSN: 0167-2738
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- Citations: 96
Bayliss RD, Cook SN, Fearn S, et al., 2014, On the oxide ion conductivity of potassium doped strontium silicates, Energy and Environmental Science, Vol: 7, Pages: 2999-3005, ISSN: 1754-5692
Recent reports of remarkably high oxygen ion conductivity in a new family of layered strontium silicates have questioned the rationale for materials design in solid electrolytes. Here, we present a re-investigation of the crystal structure, microstructure, total conductivity and perform the first direct investigation of oxygen ion diffusivity of a nominal Sr0.8K0.2Si0.5Ge0.5O2.9 composition. The results show very low levels of oxide ion conductivity, which do not correlate with total electrical conductivity. Furthermore, sub-micron elemental mapping reveals a previously unreported inhomogeneous chemical composition. The absence of evidence for secondary phases in the diffraction data suggests that the additional phases are amorphous in nature.
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