Synthèse par pulvérisation cathodique et caractérisation d'électrolytes conducteurs protoniques pour les piles à combustible de type PCFC

The recent trends in solid oxide fuel cells consist in exploiting the proton conduction through the use of perovskite structure oxides, more efficient at intermediate temperature than O2- conducting oxides. A second way of improvement of the cell performances consists in decreasing the electrolyte thickness in the range 5-10 μm in order to minimise its resistance. In this context, physical vapour deposition processes present a particular interest. In this work, we studied the feasibility of strontium or barium cerates or zirconates (BaCe1-xYxO3-a, BaZr1-xYxO3-a and SrZr1-xYxO3-a), known as the most promising proton conductor materials, by reactive magnetron co sputtering. After a description of the reactor used for the synthesis, we present the main relations between the deposition parameters and the chemical composition of the coatings. Those as deposited coatings are amorphous and their crystallisation is studied either by synthesis at high temperature or after ex situ annealing treatments. Finally, the conduction properties of the coatings of targeted composition are studied using electrochemical impedance spectroscopy and are compared to those of bulk pellets of same composition.Les tendances récentes en matière de piles à combustible à oxydes solides visent à exploiter la conduction du proton par l'utilisation d'électrolytes de structure de type pérovskite, plus performants à température modérée que les électrolytes conducteurs de l'ion oxyde. Une seconde voie d'amélioration des performances des piles consiste à diminuer l'épaisseur de l'électrolyte aux alentours de 5-10 μm pour minimiser sa résistance. Dans ce contexte, les procédés de dépôt physique trouvent un intérêt majeur. Dans ce travail, nous nous sommes attachés à étudier la faisabilité de couches denses de cérates ou de zirconates de baryum ou de strontium (BaCe1-xYxO3-a, BaZr1-xYxO3-a et SrZr1-xYxO3-a), les électrolytes conducteurs protoniques les plus aptes à répondre aux besoins de l'application, par co-pulvérisation de cibles métalliques en présence d'une atmosphère réactive d'argon-oxygène. Après une description du dispositif expérimental utilisé pour la synthèse des couches, nous étudierons plus particulièrement l'influence des paramètres de dépôt sur la composition des revêtements. Les films bruts d'élaboration étant amorphes, leur cristallisation est étudiée lors de synthèses en température ou au cours de recuits ex-situ. Enfin, les propriétés de conduction ionique des couches de composition visée sont étudiées par spectroscopie d'impédance électrochimique et comparées à celle des matériaux massifs correspondant

PVD processes for energy application

International audiencePVD processes for energy applicatio

Structural, electrical and gas sensing properties of Ag doped LaCoO3 nanowires deposited by reactive magnetron sputtering

International audienceStructural, electrical and gas sensing properties of Ag doped LaCoO3 nanowires deposited by reactive magnetron sputterin

Performances in Energy Generation And Potential Applications in Environment of Sputter Deposited Solid Electrolytes and Mixed Conductors

International audienceSolid electrolytes and mixed conductors are often complex oxides widely used in numerous applications in the fields of energy and environment such as fuel cells, microbatteries, catalysts, sensors etc. Among the methods able to allow the synthesis of these various materials, reactive co sputtering appears as an interesting and powerful alternative. This is particularly true when in situ optical methods are used to control either the deposition rate or the coating transparency. In this presentation, we will first describe the structural features of the main solid electrolytes and mix conductors which often present fluorite, perovskite or close-perovskite structures. Hence, we will discuss the deposition conditions for high rate deposition of those materials, either as dense coatings such as required for electrolyte coatings or as porous layers such as required for mix conductors in numerous applications. In each case, the relation between deposition conditions and coating morphology and structure will be established. Some examples of coating intrinsic performance owing to their ionic or electrical conductivity or catalytic activity will then be presented in relation with their deposition conditions. Finally, some recent examples of applications will be given in the fields of solid oxide fuel cells, depollution catalysts or gas sensors

Pt–Ti Alloy Coatings Deposited by DC Magnetron Sputtering: A Potential Current Collector at High Temperature

International audienceMetallic platinum–titanium coatings were deposited by co-sputtering of two metallic Pt and Ti targets in pure argon atmosphere. The titanium concentrations varied from 0 to 47 atomic percent and were adjusted as a function of the current applied to the titanium target. The structural and chemical features of these films were assessed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). All as-deposited coatings exhibit a perfect covering of the alumina pellets’ substrate surface. The coatings containing more than 4 at.% Ti are amorphous, whereas the others crystallize in the face-centered cubic (fcc) structure of platinum. After an annealing treatment under air for 2 h, all of the coatings adopt the fcc structure with a crystallization temperature depending on the titanium content. For titanium concentrations higher than 32 at.%, the TiO2 phase appears during the annealing treatment. For the smaller film thickness of Pt–Ti alloys (15 nm), the Ostwald ripening mechanism is observed by SEM increasing the annealing temperature regardless of the content of Ti. The film resistivity measured at room temperature is lower than 7 ´ 10−4 Ω·cm and increases with the temperature to achieve an insulating behavior (in air and reducing atmosphere Ar-H2 (90-10) at 1123 K the resistivity is ρ » 10+36Ω·cm). When the thickness of intermetallic Pt3Ti layer is higher than 50 nm, the coating is continuous and the resistivity is below 5 ´ 10−4 Ω·cm in air and in reducing atmosphere (Ar with 10% of H2) up to 1273

Optoelectronic properties of delafossite structure CuCr 0.93 Mg 0.07 O 2 sputter deposited coatings

International audienceCuCr0.93Mg0.07O2 thin films with improved optoelectronic properties were deposited by reactive magnetron sputtering on fused quartz substrates. The influence of annealing temperature under vacuum on optoelectronic properties of the films was investigated.The amorphous films annealed under vacuum at temperatures higher than 923K are single-phased delafossite structure, while impurity phases like CuCr2O4 that affect the optoelectronic properties of the films are detected below 873K. c-axis orientation is observed for CuCr0.93Mg0.07O2 layers and the annealing temperature window in which the films are single-phased delafossite is much larger with Mg doping (923K → 1073K) than that for undoped films (~953K). The optical and electrical behaviours of the films are enhanced by Mg substitution and their direct band gap energy of about 3.12–3.14 eV is measured. The film possesses the optimum properties after annealing under vacuum at about 1023K; its average transmittance in the visible region can reach 54.23% while the film’s conductivity is about 0.27 S cm−1

Ag composition gradient CuCr0.93Mg0.07O2/Ag/CuCr0.93Mg0.07O2 coatings with improved p-type optoelectronic performances

International audienceThe optoelectronic properties of Mg-doped CuCrO2 with delafossite structurewere enhanced by stacking CuCr0.93Mg0.07O2/Ag/CuCr0.93Mg0.07O2 multilayers.The influences of the deposition time of the Ag and the thickness of theCuCr0.93Mg0.07O2 layers on the film’s performance were investigated. When thestacks were deposited under our deposition conditions, no continuous Ag layerwas observed. The diffusion of Ag atoms into the neighboring CuCr0.93Mg0.07O2layers caused a composition gradient of Ag in the films and caused Cr3? cationsto be replaced by Ag? cations, which is beneficial for improving the conductivityof the films. When the Ag deposition time was increased, Schottky barriersoccurred between Ag nanocrystallites and CuCr0.93Mg0.07O2 grains, loweringthe films’ optoelectronic performances. The multilayers’ optoelectronic performanceswere enhanced when the thickness of the CuCr0.93Mg0.07O2 layers wasdecreased. Optimal films with a relatively high figure of merit of2.37 9 10-7 X-1 can be achieved when the deposition time of Ag and thethickness of CuCrO2:Mg layers are optimized

Catalytic Properties of Double Substituted Lanthanum Cobaltite Nanostructured Coatings Prepared by Reactive Magnetron Sputtering

Lanthanum perovskites are promising candidates to replace platinum group metal (PGM), especially regarding catalytic oxidation reactions. We have prepared thin catalytic coatings of Sr and Ag doped lanthanum perovskite by using the cathodic co-sputtering magnetron method in reactive condition. Such development of catalytic films may optimize the surface/bulk ratio to save raw materials, since a porous coating can combine a large exchange surface with the gas phase with an extremely low loading. The sputtering deposition process was optimized to generate crystallized and thin perovskites films on alumina substrates. We found that high Ag contents has a strong impact on the morphology of the coatings. High Ag loadings favor the growth of covering films with a porous wire-like morphology showing a good catalytic activity for CO oxidation. The most active composition displays similar catalytic performances than those of a Pt film. In addition, this porous coating is also efficient for CO and NO oxidation in a simulated Diesel exhaust gas mixture, demonstrating the promising catalytic properties of such nanostructured thin sputtered perovskite films

Reactive magnetron sputtered BiVO4 thin film as an efficient visible light photocatalyst

International audience