J.C.H. Rossiny

Imperial College London, London, ENG, United Kingdom

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Publications (10)17.07 Total impact

  • J. A. Kilner, A. Berenov, J. Rossiny
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    ABSTRACT: There are a large number of complex metal oxides, with the general formula ABO3, that form into the many and closely related perovskite-type structures. These materials show a very wide range of valuable physicochemical properties including ferromagnetism, catalytic activity, ferroelectricity, giant magneto-resistive effect, and ionic and mixed conductivity. As just mentioned, there are a number of structure types that fall under the collective name of perovskite, including the ideal cubic structure, rhombohedral, tetragonal, and orthorhombic distortions, and the hexagonal GdFeO3 types. In this chapter, we present a review of the literature on the subject of oxygen ion diffusion in these materials, as this is fundamental to an understanding of the other physical properties. This is a limited review, as the literature on this subject is extensive, and the aim here is to present the trends that will aid in understanding the changes in oxygen transport between different compositions and materials under different conditions. To this end, the structural differences in the materials will be ignored to a first approximation, and this must be remembered when the comparisons of data are being made. One of the fundamental difficulties in following the trends that occur in the diffusivity of oxygen is the inherent multidimensional nature of the data for the materials concerned. For example, the diffusivity is dependent upon temperature, oxygen partial pressure, identity of the A and B cations, the degree of substitution on either the A or B sites, and finally any deviations from the ideal A to B 1:1 occupancy ratio.
    06/2009: pages 95-116;
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    ABSTRACT: We present work on the creation of a ceramic materials database which contains data gleaned from literature data sets as well as new data obtained from combinatorial experiments on the London University Search Instrument. At the time of this writing, the database contains data related to two main groups of materials, mainly in the perovskite family. Permittivity measurements of electroceramic materials are the first area of interest, while ion diffusion measurements of oxygen ion conductors are the second. The nature of the database design does not restrict the type of measurements which can be stored; as the available data increase, the database may become a generic, publicly available ceramic materials resource.
    Journal of Chemical Information and Modeling 03/2008; 48(2):449-55. · 4.30 Impact Factor
  • Sarah Fearn, Jeremy Rossiny, John Kilner
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    ABSTRACT: Using ultra low energy SIMS ion beams of oxygen and nitrogen, the very near surface region of an 16O annealed La0.8Sr0.2MnO3 pellet has been depth profiled in order to investigate the surface layer composition and to determine any perturbing ion beam–target interactions. By ratioing the measured cation species, the results indicate that only Sr segregation at the near surface can be clearly identified, and no separate oxide layer was present on the top surface. By monitoring the build up of the altered layer associated with SIMS depth profiling, it was observed that the depth at which the altered layer was fully formed was deeper than the expected projected range, Rp, of the ion beam. These results confirm Sr excess in the near surface, which will have an effect on the vacancy concentration and therefore the surface exchange coefficient, k.
    Solid State Ionics 01/2008; 179:811-815. · 2.05 Impact Factor
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    ABSTRACT: The Rare-Earth ferrates REFeO3 (RE=La, Pr, Sm, Gd, Ho) were prepared by the citric acid route. The distortion in the FeO6 octahedron decreased with the decrease in the ionic radii (except for Ho) and the angle between adjacent FeO6 octahedra decreased with the ionic radius of the rare earth. Electrical conductivity showed semiconducting behaviour with a complex dependence of the activation energy on the ionic radii of RE ion. Fast oxygen desorption was observed above 300 °C. No effect of A-site cation on the coefficients of thermal expansion was observed.
    Solid State Ionics 01/2008; 179(21):1090-1093. · 2.05 Impact Factor
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    ABSTRACT: One of the most common types of structure which displays Mixed Electronic Ionic Conductivity is the ABO3 perovskite. The perovskite structure defines a very large range of possible oxide compositions and thus, for screening as potential SOFC cathodes, new methods must be used to obtain a complete picture of these MIEC materials. Combinatorial methods offer a route to identify the major trends in functional properties prior to full scale experiment. The system La1−xSrxCo1−y−zMnyFezO3+δ (LSCMF) has been synthesised by combinatorial methods using a robot ink-dip printer. A systematic set of experiments was performed to characterise the trends in crystal structure, and non-stoichiometry with composition. It is the first time that this LSCMF pseudo-ternary has been measured with a 10% B-site substitution of cobalt, manganese and iron.
    Solid State Ionics 01/2008; 179(21):1085-1089. · 2.05 Impact Factor
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    ABSTRACT: We describe the development of artificial neural networks (ANN) for the prediction of the properties of ceramic materials. The ceramics studied here include polycrystalline, inorganic, non-metallic materials and are investigated on the basis of their dielectric and ionic properties. Dielectric materials are of interest in telecommunication applications where they are used in tuning and filtering equipment. Ionic and mixed conductors are the subjects of a concerted effort in the search for new materials that can be incorporated into efficient, clean electrochemical devices of interest in energy production and greenhouse gas reduction applications. Multi-layer perceptron ANNs are trained using the back-propagation algorithm and utilise data obtained from the literature to learn composition-property relationships between the inputs and outputs of the system. The trained networks use compositional information to predict the relative permittivity and oxygen diffusion properties of ceramic materials. The results show that ANNs are able to produce accurate predictions of the properties of these ceramic materials which can be used to develop materials suitable for use in telecommunication and energy production applications.
    04/2007;
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    S. Fearn, J.C.H. Rossiny, J.A. Kilner, Y. Zhang, L. Chen
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    ABSTRACT: Conventional synthesis of ceramic oxide compositions is time consuming and consequently limits the compositions that can be studied. A way round this is the use of combinatorial methods to explore much wider ranges of compositions. Using an inkjet based robot system; London University Search Instrument (LUSI) combinatorial arrays of ceramic dot samples can be produced. The first part of the study consists of the characterisation of a printed array of La0.8Sr0.2CoO3−δ to ensure the reproducibility and quality of the ceramic dots and suitability for isotopic exchange experiments.
    Applied Surface Science 01/2006; 252(19):7159-7162. · 2.54 Impact Factor
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    J C H Rossiny, S Fearn, J A Kilner, Y Zhang, L Chen
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    ABSTRACT: Conventional synthesis of ceramic oxide compositions is time consuming and consequently limits the compositions that can be studied. A way round this is the use of combinatorial methods to explore much wider ranges of compositions. Using an inkjet based robot system, LUSI (London University Search Instrument) combinatorial arrays of ceramic dot samples can be produced. The first part of the programme consists of the characterisation of a printed array of La 0.8 Sr 0.2 CoO 3−δ to ensure the reproducibility and quality of the ceramic dots and suitability for isotopic exchange experiments. Simulation of the oxygen exchange with a ceramic dot sample to predict the distribution of oxygen within the dot has also been performed.
    Solid State Ionics. 01/2006; 177(19).
  • S. Fearn, J.C.H. Rossiny, J.A. Kilner, J.R.G. Evans
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    ABSTRACT: In this work values for the diffusion coefficient, D*, and surface exchange coefficient, k*, have been obtained from individual La0.8Sr0.2MnO3 perovskite grains. Oxygen tracer diffusion profiles were created via the well established isotope exchange techniques. The tracer diffusion profiles were then measured using a FIB-SIMS workstation. Several measurements were taken over randomly selected grains including un-faceted and faceted grains. The values for D* and k* obtained compared very well with previous measurements made on bulk La0.8Sr0.2MnO3 samples i.e. over many grains. The results therefore indicate that D* and k* are independent of orientation. Furthermore the diffusion profiles indicated that only one single grain had been SIMS depth profiled and did not cross a grain boundary. Also by analysing in the centre of large grains, and not analysing up to the edge of the grains, no grain boundary diffusion was observed. Finally, the work also confirms that previous measurements of k* on this material have been correctly measured and not under estimated due to experimental errors.
    Solid State Ionics 211:51–57. · 2.05 Impact Factor
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    ABSTRACT: The mixed conducting perovskite-type La0.8Sr0.2Co1 − yMnyO3 ± δ family has been synthesised by a combinatorial method. This system including the two end member materials (y = 0 and 1) have been studied using temperature programmed methods in order to relate structure and composition to oxygen exchange under a hydrogen atmosphere. Oxygen is removed in two steps: firstly, labile surface oxygen from 350 to 450 °C and then more strongly bound lattice oxygen. A relationship between the B-site manganese and cobalt content and ease of removal of lattice oxygen was demonstrated over the temperature range of 600–820 °C. Removal of labile surface oxygen was independent of the B-site composition but associated with A-site cations on the external surface of the crystallites.
    Solid State Ionics 225:182–185. · 2.05 Impact Factor