Synthesis of La2NiO4+d oxides by sol–gel process: Structural and microstructural evolution from amorphous to nanocrystallized powders

In this paper, the structural and microstructural transition from amorphous to La2NiO4+d nanocrystallized oxides synthesized by a polymeric route based on Pechini’s work has been studied by several experimental techniques including infrared spectroscopy and wide angle X-ray scattering. The synthesis parameters which govern this transition have been identified in order to synthesize La2NiO4+d oxides with various mean crystallite sizes and non stoichiometry levels. Therefore, it has been demonstrated that the control of the nature and the content of organic compounds in the polymeric sols allows the preparation of La2NiO4+d metastable phases with a mean crystallite size ranging from 100 to 220 nm and a non stoichiometry level ranging from 0.15 to 0.22 at 25 8C. As the cathodic performance strongly depends on the physical characteristics of the oxides, this study shows that our versatile process may be suitable to elaborate electrodes with different electrochemical behaviours

Preparation of Ni–YSZ thin and thick films on metallic interconnects as cell supports. Applications as anode for SOFC

In this work, we propose the preparation of a duplex anodic layer composed of both a thin (100 nm) and a thick film (10 lm) with Ni–YSZ material. The support of this anode is a metallic substrate, which is the interconnect of the SOFC unit cell. The metallic support limits the temperature of thermal treatment at 800 C to keep a good interconnect mechanical behaviour and to reduce corrosion. We have chosen to elaborate anodic coatings by sol–gel route coupled with dip-coating process, which are low cost techniques and allow working with moderate temperatures. Thin films are obtained by dipping interconnect substrate into a sol, and thick films into an optimized slurry. After thermal treatment at only 800 C, anodic coatings are adherent and homogeneous. Thin films have compact microstructures that confer ceramic protective barrier on metal surface. Further coatings of 10 lm thick are porous and constitute the active anodic material

Potentiometric selectivity and impedance characteristics of a NASICON-based ion selective electrode

International audienc

Electrochemical Characterisation Of Thin And Dense Yttria Stabilised Zirconia Electrolyte Coatings Elaborated By Physical Vapour Deposition

International audienc

Effect of high-content Yttria on the thermal expansion behaviour and ionic conductivity of a stabilised cubic Hafnia

The needs for space propulsion thruster induce the development of new designs and material compositions able to withstand 3000 K of flame combustion temperature. Cubic-stabilised hafnia appears as one of the most promising candidates to protect refractory materials in such conditions. Here, the influence of dopant content on the thermal expansion (473−1823 K) and ionic conductivity (600−1150 K) in highly doped-hafnia (12−33 mol% Y2O3) with disordered cubic systems is reported. The composition and the homogeneity of the samples were carefully checked using crystallographic, chemical and spectroscopy analyses. Finally, the study of thermal and oxygen conductivity properties highlighted their dependence on the amount of dopant. The average thermal expansion coefficient was lowered from 11.3 to 10.9 10−6/K and the ionic conductivity decreased by two decades with 33 mol% of Y2O3 by using the optimised substitution ratio. Interactions and local ordering of oxygen vacancies can explain this behaviour

Hydration properties and rate determining steps of the oxygen reduction reaction of perovskite-related oxides as H+-SOFC cathodes

Four mixed ionic-electronic conducting (MIEC) perovskite-related oxides were studied as potential H+-SOFC cathode materials: La0.6Sr0.4Fe0.8Co0.2O3−, Ba0.5Sr0.5Co0.8Fe0.2O3−, PrBaCo2O5+ and Pr2NiO4+. Their hydration properties were measured by TGA: Ba0.5Sr0.5Co0.8Fe0.2O3− shows the largest water uptake. Their electrochemical performances were characterized using BaCe0.9Y0.1O3− as electrolyte; polarization resistances as low as 0.5 cm2 were found at 600°C, for PrBaCo2O5+ and Pr2NiO4+. The rate determining steps of the oxygen reduction reaction were determined on the basis of electrochemical studies performed as a function of pH2O, in air. Proton transfer and water release appear to be the rate determining steps for Ba0.5Sr0.5Co0.8Fe0.2O3−, PrBaCo2O5+ and Pr2NiO4+. No rate determining step involving proton was found for La0.6Sr0.4Fe0.8Co0.2O3−. On the basis of this study, one can suggest that Ba0.5Sr0.5Co0.8Fe0.2O3−, PrBaCo2O5+ and Pr2NiO4+ show some protonic conduction as well as oxide diffusivity and can be labeled Triple Conducting (e-/O2−/H+) Oxides, so-called TCO