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In this paper, we derive an accurate power model for video streaming which we condense to the essential components contributing the most to the overall power consumption. As a use case, we choose mobile devices on the receiver side performing video streaming in broadcasting or end-to-end scenarios. In modeling, we consider the complete video streaming toolchain, which mainly consists of data acquisition, video processing, display, and audio handling. We compose an overall power model with the help of models from the literature and propose a dedicated feature selection approach to reveal the most important factors related to power consumption. The resulting models achieve mean estimation errors below 7.61%. Results from feature selection indicate that the display brightness, the bitrate, and the frame rate have the highest impact on the power consumption.

The kinetics and mechanism of oxygen reduction reaction (ORR) in alkaline medium are studied on lanthanum nickelate materials La 2−x−y Nd x Pr y NiO 4±δ (x = 0, 0.3 and 0.5; y = 0 and 0.2) using the electrochemical technique of the rotating disk electrode in a 0.5-M solution of NaOH. The oxide powders are synthesized by the citrate–nitrate method. Structural and surface characterizations are performed by X-ray diffraction (XRD) and X-ray photoelectron spectrometry (XPS), while the morphology is studied by scanning electron microscopy (SEM). Electrochemical studies are carried out by linear voltamperometry, cyclic voltamperometry, and impedance spectroscopy. The doped and undoped electrocatalyst composites (La 2−x−y Nd x Pr y NiO 4±δ /C), made of the rare earth nickel oxides mixed with carbon black (Vulcan XC-72(C)), are deposited as a thin layer on a glassy carbon substrate. At room temperature, the undoped electrocatalyst La 2 NiO 4±δ material shows single-step kinetics unlike the doped materials. The doping by the rare earths Nd or/and Pr significantly enhances the electrical conductivity of the electrode under air and the diffusion of oxygen. On the other hand, the steric hindrance between the atomic oxygen orbital (π-orbital (O 2 )–π-orbital (O 2 )) and the dz 2 –orbital (Ni)–π-orbital (O 2 ) influences the training model of the liaison (dz 2 (Ni)–π (O 2 )). The structure, oxygen adsorption, and oxidation states of the catalyst elements have a large influence on the mechanism and kinetics of the ORR. The LNNO3/C and LNPNO5/C electrocatalysts have better electrocatalytic performances, which allow them to be used as a bifunctional electrocatalyst for the reduction of oxygen in alkaline media.

Compositions in the La2−xPrxNiO4+δ series offer an attractive balance of chemical stability and electrochemical performance for use as cathode materials in solid oxide fuel cells (SOFCs). A detailed crystallographic study of this system has been performed, combining both high resolution synchrotron and neutron powder diffraction data, in order to investigate structural details of the series as a function of composition, temperature and oxygen over-stoichiometry. The monoclinic structure (space group F2/m) of ambient temperature Pr-rich compositions for 1.0 < x ≤ 2.0 is discussed in terms of octahedra tilt arrangements and possible long-range structural modulations. In situ synchrotron diffraction experiments and TEM are employed to examine the role of temperature and interstitial oxygen on these structural distortions. With increasing La substitution, a region of mixed monoclinic and tetragonal phases is described for 0.5 ≤ x ≤ 1.0. La-Rich compositions are found to be single phase tetragonal (F4/mmm for 0 < x < 0.5) or orthorhombic (Fmmm for x = 0). Possible origins and electrochemical property consequences of the refined structural trends are considered.

International audience; This paper reports the study of the densification of 20% Gd doped ceria (Ce0.8Gd0.2O1.9 (GDC)) interlayers in SOFC cathodes through two different routes: the well-known addition of sintering elements, and an innovative densification process by infiltration. First, Li, Cu, and Zn nitrates were added to GDC powders. The effect of these additives on the densification was studied by dilatometry on pellets, and show a large decrease of the sintering temperature from 1330 °C (pure GDC), down to 1080 °C, 950 °C, and 930 °C for Zn, Cu, and Li addition, respectively. However, this promising result does not apply to screen-printed layers, which are more porous than pellets and in which the shrinkage is constrained by the substrate. The second approach consists in preparing a pre-sintered GDC layer, which is subsequently infiltrated with Ce and Gd nitrates and sintered at 1250 °C to increase its density. Such an approach results in highly dense GDC interlayers. Using La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) as electrode, the influence of the interlayers on the cathode performance was studied. The addition of sintering aids dramatically increases the cell resistances, most likely because the additives increase the reactivity between GDC and either Yttria Stabilized Zirconia (YSZ) or LSCF, thus losing the expected benefit related to the decrease of sintering temperatures. The interlayers prepared by infiltration do not induce additional resistances in the cell, which results in power densities of single cells 40–50% higher than those of cells prepared with commercial GDC interlayers, making this approach a valuable alternative to sintering aids.

International audience; PrBa2Cu3O6+δ (P) and PrBa1.5Sr0.5Cu3O6+δ (PS) layered perovskite-type oxides are synthesized and characterized as oxygen electrodes in IT-SOFCs. The layered structure of P and PS compounds is constituted by the regular alternation along the crystallographic c axis of PrO planes, Cu2+ chains (CN = 4) and Cu3+ pyramidal (CN = 5) layers. Interesting features of the PrBa2Cu3O6+δ structure are the absence of cobalt, the presence of aliovalent cations and large amounts of oxygen vacancies. The substitution of 25% Ba with Sr is evaluated in order to improve the electronic conductivity of the undoped material. The compounds are synthesized via Citrate-Nitrate procedure and characterized by XRPD, 4-probe conductivity tests (100–800 °C) and EIS measurements on symmetric cells in air varying the temperature (450–850 °C). SEM images of post mortem cells are collected to evaluate the adhesion between components, layers thickness and particle morphology. Sr doping does not significantly improve the electrical conductivity but prompts a considerable hysteresis in the P sample between the cooling and the heating ramps. Conductivity values are lower than 100 S cm−1, but no electrical limitations are observed in EIS results. The introduction of a thin PrDC interlayer greatly reduces the Area Specific Resistances for both the compounds and the 0.15 Ω cm2 target is almost fulfilled at 600 °C (0.17 Ω cm2 for PS + PrDC sample).

International audience; The oxygen reduction reaction (ORR) was studied using Nd1.9Sr0.1Ni0.9Co0.1O4 ± δ (NSNCO01) nickelates as cathode material at room temperature in aqueous phase. The citrate method was used for preparing the material. The electrochemical study of ORR was carried out in a 0.5-M NaOH solution at 25 °C with a rotating disk electrode. XRD and SEM analysis were performed to characterize the crystallinity of the material. XPS analysis is used to evaluate the surface state of the material. Electrochemical studies were followed by linear voltammetry and impedance spectroscopy measurements. The electrocatalyst composite Nd1.9Sr0.1Ni0.9Co0.1O4 ± δ/C, consisting of oxide nickelate and carbon (Vulcan XC-72), was mixed and deposited as a layer on a glassy carbon substrate. At room temperature, a significant electrocatalytic activity is observed for the studied material that shows a relatively high electrocatalytic activity for O2 reduction.

International audience; The mean oxidation state of cationic elements in Pr2NiO4+δ was studied using XANES measurements versus temperature in air. Unexpectedly, praseodymium is solely found as Pr3+ while Pr4+ was also foreseeable. Pr3+ cation is well accommodated in the large rare-earth site with the nine-fold coordination in this K2NiF4 – T-type structure; conversely, the small size of the Pr4+ cation seems not compatible with this site. Moreover, XANES measurements show a progressive decrease of the mean oxidation state of nickel ions when the temperature increases. It is directly correlated to the decrease of the oxygen over-stoichiometry of the material evidenced by TGA measurements.

Sr-doped double perovskite oxides PrBa 1− x Sr x Co 2 O 5+ δ ( x = 0.0–1.0) are prepared and characterized by X-ray diffraction, X-ray photoelectron spectra, cyclic voltammetry and linear sweep voltammetry, respectively. Sr 2+ doping is found to promote the electrocatalytic activity towards both oxygen evolution reduction and oxygen reduction reaction, due to the concentration enhancement of Co 4+ (e g = 1) on the oxide surface. The PrBa 0.25 Sr 0.75 Co 2 O 5.95 catalyst, with the highest concentration of Co 4+ , exhibits the superior electrocatalytic activity. The onset potential, Tafel slope and the overpotential at given current density of 10.0 mA·cm geom −2 for the OER are 1.52 V, 75.8 mV·dec −1 and 0.42 V, respectively, comparable to the currently reported high performance OER catalysts. At the same time, the onset potential, Tafel slope, limiting current density and electron transfer number of PrBa 0.25 Sr 0.75 Co 2 O 5.95 for ORR are 0.753 V, 58.3 mV·dec −1 , 4.081 mA·cm geom −2 and n = 3.92, respectively, implying much improved ORR activity.

The peculiar structure of PrBa2Cu3O6+δ (Pr123) consists of Pr-O, Cu2+ chains (CN = 4) and Cu3+ pyramidal (CN = 5) layers, regularly alternated along the c axis. Different issues related to material instability were investigated producing samples of same composition, but of different thermal history. Rietveld refinements revealed the copresence of two Pr123 phases: a tetragonal one (Pr123-T), stable at high temperatures, and an orthorhombic phase (Pr123-O), resulting from the oxidation of Pr123-T below 750-700 °C. The Pr123 samples produced with different calcination cooling rates showed that different O/T ratios influence the oxygen content (6+δ), the electrical conductivity and the polarization resistances. EIS tests were performed on symmetrical electrolyte supported cells with PrDC30 interlayer, starting the measurements at 500 °C, then increasing up to 700 °C. Promising ASR values were obtained for these compounds, with different activation energies, which indicated different ORR mechanisms.

International audience; The performances of mixed ionic and electronic conductors is used in many applications, such as oxygen transport membranes or electrodes in solid oxide fuel cells. The performances of these systems depend mainly on two fundamental parameters including oxygen diffusion (DO) and the oxygen exchange coefficient (k). This work focuses on the impact of the oxygen partial pressure on oxygen diffusion and surface exchange coefficients of mixed conducting materials, as reported studies are scarce in the literature. In this way, two different mixed conducting materials are studied, namely, La0.6Sr0.4Fe0.6Ga0.4O3-δ, a perovskite-type material, and the nickelate La2NiO4+δ. The DO and k coefficients are determined by a specific oxygen permeation measurement and by the isotopic exchange depth profile method.

Compositions in the La2-xPrxNiO4+δ series offer an attractive balance of chemical stability and electrochemical performance for use as cathode materials in solid oxide fuel cells (SOFCs). A detailed crystallographic study of this system has been performed, combining both high resolution synchrotron and neutron powder diffraction data, in order to investigate structural details of the series as a function of composition, temperature and oxygen over-stoichiometry. The monoclinic structure (space group F2/m) of ambient temperature Pr-rich compositions for 1.0x ≤ 2.0 is discussed in terms of octahedra tilt arrangements and possible long-range structural modulations. In situ synchrotron diffraction experiments and TEM are employed to examine the role of temperature and interstitial oxygen on these structural distortions. With increasing La substitution, a region of mixed monoclinic and tetragonal phases is described for 0.5 ≤ x ≤ 1.0. La-Rich compositions are found to be single phase tetragonal (F4/mmm for 0x0.5) or orthorhombic (Fmmm for x = 0). Possible origins and electrochemical property consequences of the refined structural trends are considered.

International audience; The praseodymium nickelate PrNiO3-δ was recently identified as one of the decomposition products of Pr2NiO4+δ oxygen electrode, raising the question of the role of this perovskite compound on the Pr2NiO4+δ performance and ageing behaviour. Herein, the electrochemical properties of PrNiO3-δ as cathode for Solid Oxide Fuel Cells (SOFCs) is reported. PrNiO3-δ, synthesized from the citrate-nitrate route, cristallizes in an orthorhombic structure (S.G.: Pnma). Under air, a transition to high temperature rhombohedral structure (S.G.: R-3c) occurs at around 600 °C, while its oxygen vacancy amount increases from δ 0.05 at room temperature up to 0.10 at high temperature. Thermal gravimetry analysis (TGA) measurements coupled with X-ray diffraction (XRD) characterizations show that above 1000 °C, in air, PrNiO3-δ starts to decompose into Pr2NiO4+δ and NiO through an intermediate transformation into Pr4Ni3O10+δ. The value of the polarization resistance (Rp) of co-sintered GDC-PrNiO3-δ electrode, at 950 °C in air for 2 h, is 0.91 Ω cm2 at 600 °C under air. It remains much higher than that of co-sintered GDC-Pr2NiO4+δ electrode (Rp = 0.15 Ω cm2), which means that the perovskite does not play any significant role in the electrochemical performance during long term operation of the Pr2NiO4+δ electrode

International audience; The double perovskite oxides La2-xNiMnO6-δ (x = 0.0, 0.1, 0.2, 0.3) are evaluated as potential cathodes for intermediate temperature solid oxide fuel cells. The effects of La-deficiency on the crystal structure, high temperature thermal and electrical properties, and catalytic activity for oxygen reduction reaction are comprehensively investigated. La2-xNiMnO6-δ crystallizes in monoclinic structure with the space group P21/n. The cell volume expands with the increase of La-deficiency. The highest electrical conductivity of 25 S cm−1 is found for La1.8NiMnO5.71 at 800 °C in air. Introducing La3+ deficiency greatly improves the amount of chemical adsorbed oxygen species on material surface, which promotes the oxygen reduction reaction of La2-xNiMnO6-δ cathode. The optimum composition, La1.8NiMnO5.71 exhibits the lowest area specific resistance of 0.21 Ω cm2 at 700 °C in air. Meanwhile the peak power density of the anode-supported single cell with La1.8NiMnO5.71 cathode reaches 0.6 W cm−2 at 700 °C. The electrochemical impedance spectra measurements combining with distribution of relaxation times analysis prove that the charge transfer process is the rate-limiting step of the ORR reaction.

International audience; Electrochemical impedance spectroscopy measurements carried out on La2NiO4+δ(LNO)//Ce0.8Gd0.2O2−δ(GDC)//3mol.%Y2O3-ZrO2(TZ3Y) half-cells from 500°C to 800°C revealed that the impedance of the LNO electrode is Gerischer-like. Based on experimental data of the porosity, tortuosity, surface area, molar volume and thermodynamic factor of the LNO electrode sintered at 1200°C, the ionic conductivity σi(LNO) and the surface exchange coefficient ℜ0 of the LNO electrode are calculated using the Adler-Lane-Steele (ALS) model. Surprisingly, the polarization resistance of the half-cell is shown to depend on the sintering temperature of the GDC interlayer, which is varied from 1200°C up to 1450°C. Whatever the sintering conditions of GDC, the calculated ℜ0 values agree with those obtained by recently published pulse isotopic exchange (PIE) experiments. Indeed, the oxygen reduction reaction mostly occurs at the LNO grain surface. However, the calculated ionic conductivity of the electrode vary depending on the GDC sintering temperature. X-ray diffraction studies of the LNO//GDC and GDC//TZ3Y interfaces reveal that cations interdiffusion occurs in both cases. The interfacial GDC layer may act as a bottleneck for the oxide ion transfer from the LNO electrode toward the TZ3Y electrolyte, and vice-versa, resulting in an increase of the series and polarization resistances.

International audience; This paper is devoted to the study of composite cathodes of La2NiO4+δ infiltrated into a Gd-doped ceria backbone. Porous Gd-doped ceria backbones are screen printed onto yttria-stabilized zirconia or Gd-doped ceria dense electrolytes, and infiltrated with a La and Ni nitrate solution (2:1 stoichiometry ratio). The influence of the preparation parameters on the polarization resistance, such as the concentration of the infiltration solution, the amount of infiltrated phase, the annealing temperature, the thickness of the electrode, and the nature of the electrolyte, is characterized by impedance spectroscopy performed on symmetrical cells. The optimization of these parameters results in a decrease of the polarization resistance down to 0.15 Ω cm2 at 600 °C. Using the Adler-Lane-Steele model, the modelling of the impedance diagrams leads to the determination of the ionic conductivity as well as the surface exchange rate of the infiltrated electrode.

The present study is focused on alternative oxygen electrodes for Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFCs) using Metal Supported Cells (MSCs) conditions. To prevent detrimental oxidation of the metal support, sintering of the cell components at high temperature under low pO2 is required. Ln2NiO4+δ (Ln = La, Pr) compounds with the K2NiF4-type structure act as cathode materials for IT-SOFC due to their mixed ionic and electronic conductivity (i.e. MIEC properties). Pr2NiO4+δ shows excellent electrochemical properties at intermediate temperature (i.e. low polarization resistance Rp value, Rp = 0.03 Ω.cm² at 700 °C), while La2NiO4+δ exhibits higher chemical stability. Thus, the properties of La2 -x Pr x NiO4+δ mixed nickelates were investigated with the aim to find best compromise between chemical stability and electrochemical performances. Herein, the chemical stability of the nickelates under air at operating temperatures as well as the evolution of the polarization resistances during ageing (recorded under air at idc = 0 and idc ≠ 0 conditions) were studied for duration up to one month. La2NiO4+δ is chemically stable whereas Pr2NiO4+δ dissociates after 1 month at 600, 700 and 800 °C. At idc = 0 condition, the ageing of the half cells during 1 month under air shows no change in Rp , despite their various degrees of chemical stability. A different behavior is observed under idc ≠ 0 conditions with a large increase in Rp for Pr-rich phases in SOFC mode while interestingly, Rp remain stable in SOEC mode. In this presentation, the electrochemical properties of La2 -x Pr x NiO4+δ under ageing and postmortem analysis will be discussed in details.

International audience; The perovskite oxide Bi0.5Sr0.5Fe0.90Sb0.10O3−δ (BSFS) is evaluated as an efficient Fe-based cathode for low-temperature solid oxide fuel cells (LT-SOFCs). The BSFS material possesses a single cubic perovskite structure. The Sb-doping strategy is proven to be beneficial towards the structure stability of pristine Bi0.5Sr0.5FeO3−δ. A BSFS cathode shows an efficient electrocatalytic activity for the oxygen reduction reaction (ORR). The lowest polarization resistance (Rp) value of 0.098 Ω cm2 is obtained and the anode supported fuel cell gives a remarkable peak power density of 0.95 W cm2 at 600 °C, which is comparable to that of state-of-the-art Co-based materials. The prominent performance is ascribed to the comparable TEC value and the large amount of oxygen vacancies generated at high temperatures. Moreover, the BSFS cathode also exhibits excellent CO2 tolerance under exposure to 10 vol% CO2 at 600 °C for 24 h. These features highlight the potential applicability of the BSFS material as a highly promising cathode material for LT-SOFCs.

International audience; Cobalt-free provskite oxides Bi0.5Sr0.5Fe1−xNbxO3−δ (BSFNx, x = 0.05, 0.10 and 0.15) were prepared and evaluated as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). In particular, the effects of Nb substitution on phase evolution, thermal expansion behavior and electrochemical performance were systematically investigated. The average thermal expansion coefficient (TEC) of BSFNx decreases from 13.3 × 10−6 K−1 at x = 0.05 to 12.6 × 10−6 K−1 at x = 0.15 within a temperature range of 50–800 °C. Among the BSFNx materials, Bi0.5Sr0.5Fe0.9Nb0.1O3−δ (BSFN0.10) oxide shows the best electrochemical performance. The polarization resistances (Rp) of BSFN0.10 cathode on CGO electrolyte are 0.038, 0.075 and 0.156 Ω cm2 at 700, 650 and 600 °C, respectively. Meanwhile the maximum power densities of the anode-supported single cells are 1.28, 1.54 and 1.34 W cm−2 at 700 °C for BSFNx cathodes with x = 0.05, 0.10, and 0.15, respectively. Furthermore, the relationship study of oxygen partial pressure dependence on Rp indicates that the oxygen reduction reaction (ORR) rate-limiting step is the oxygen adsorption-dissociation on the electrode surface. The desirable electrochemical performance demonstrates that BSFNx oxides are potential cathode materials for IT-SOFCs.

International audience; The electrochemical properties of La0.6Sr0.4Co0.2Fe0.8O3−δ and Pr2NiO4+δ electrodes screen-printed on La0.8Sr0.2Ga0.8Mg0.2O2.8 and Ce0.9Gd0.1O1.95, respectively, have been investigated by electrochemical impedance spectroscopy (EIS). A study of the heat treatment of La0.6Sr0.4Co0.2Fe0.8O3−δ material used as oxygen electrode associated to La0.8Sr0.2Ga0.8Mg0.2O2.8 electrolyte was performed. The La0.6Sr0.4Co0.2Fe0.8O3−δ porous electrode sintered at 900 °C for 1 h in air exhibits the lowest cathodic polarization resistance; i.e. R P = 0.12 Ω cm2 at 600 °C. The SEM images show that the La0.6Sr0.4Co0.2Fe0.8O3−δ electrode structure is highly porous, facilitating the gas diffusion and maximizing the number of active sites for the oxygen reduction reaction (ORR). Furthermore, it forms good contact with the electrolyte after this heat treatment. In order to characterize the oxygen electrode reaction of La0.6Sr0.4Co0.2Fe0.8O3−δ and Pr2NiO4+δ , the electrochemical impedance spectroscopy (EIS) measurements were performed at temperatures between 400 and 700 °C and at different oxygen partial pressures (pO2) ranging in between 10−3 and 0.21 atm. Analysis of the impedance data revealed that there are two different processes involved in the cathode reaction. The first process in the medium-frequency range is assigned to the oxygen surface exchange reaction at the electrode/gas interface and possibly to the ionic diffusion in the material for La0.6Sr0.4Co0.2Fe0.8O3−δ and to the dissociation of the adsorbed molecular oxygen for Pr2NiO4+δ . The second one at low frequency is associated to the gas phase diffusion for both cathodes. The exchange current density, i 0, allows evaluating the electrocatalytic activity of the cathode materials. The La0.6Sr0.4Co0.2Fe0.8O3−δ /La0.8Sr0.2Ga0.8Mg0.2O2.8 couple shows the largest i 0 value, reaching 432 mA cm−2 at 700 °C and suggesting a high electrochemical activity for the O2 reduction reaction.

The layered perovskite PrBaxCo2O5+δ (PBxCO, x = 0.90–1.0) oxides have been synthesized by a solid-state reaction technique, and evaluated as the potential cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Room temperature X-ray diffraction patterns show the orthorhombic structures which double the lattice parameters from the perovskite cell parameter as a ≈ ap, b ≈ ap and c ≈ 2ap (ap is the cell parameter of the primitive perovskite) in the Pmmm space group. There is a good chemical compatibility between the PBxCO cathode and the Ce0.9Gd0.1O1.95 (CGO) electrolyte at 1000 °C. The electrical conductivity and thermal expansion coefficient of PBxCO are improved due to the increased amount of electronic holes originated from the Ba-deficiency. The results demonstrate the high electrochemical performance of PBxCO cathodes, as evidenced by the super low polarization resistances (Rp) over the intermediate temperature range. The lowest Rp value, 0.042 Ω cm2, and the cathodic overpotential, −15 mV at a current density of −25 mA cm−2, are obtained in the PrBa0.94Co2O5+δ cathode at 600 °C in air, which thus allow to be used as a highly promising cathode for IT-SOFCs. A CGO electrolyte fuel cell with the PrBa0.94Co2O5+δ cathode presents the attractive peak power density of ∼1.0 W cm−2 at 700 °C. Furthermore, the oxygen reduction kinetics of the PrBa0.94Co2O5+δ cathode is also studied, and the rate-limiting steps for oxygen reduction reaction are determined at different temperatures.

In order to clearly identify the rate determining step (rds) in oxygen semi-permeation of dense Ln2NiO4+δ membranes (with Ln = La, Pr and Nd), a specific setup has been designed, which allowed measuring the oxygen semi-permeation flux as well as the oxygen activity gradient at both membrane surfaces. From the results of the measurements, the coefficients of oxygen diffusion and surface exchange at both membrane surfaces have been determined. Their values have been compared with the values reported in the literature for similar membrane materials. The main conclusion is that the oxygen flux through these membranes is limited by the oxygen surface exchange at the oxygen-lean face, and not, as previously claimed, by oxygen volume diffusion.

The third generation of IT-SOFCs concerns the metal supported cells. With respect to the sintering conditions of the complete cell, a current challenge is the chemical stability of the components, more especially the cathode, under low pO2 (e.g. under N2, pO2 ≈ 10-4 atm). In this scope, the properties of the mixed rare earth nickelates formulated Pr2-xLaxNiO4+δ have been studied; indeed Pr2NiO4+δ is a very promising material in terms of electrochemical properties while La2NiO4+δ exhibits a higher chemical stability. The aim of this study is to find the best compromise between both characteristics. The properties of mixed phases were found intermediate between those of Pr2NiO4+δ and La2NiO4+δ.

Metal supported cells (MSC) are considered as the next generation of Solid Oxide Fuel Cells due to their robustness and cost-efficiency. However, improvement of their performances for operation below 700°C is a key point, as well as their durability and their manufacturing route. Within the RAMSES EU project, materials, components and processes have been tailored for MSCs. Thus, a metal substrate, with coating, has been optimized, fulfilling the targets of low-cost, sinterability in low-oxidizing atmosphere and oxidation resistance. A customized electrolyte powder allowed decreasing the sintering temperature of 100°C compared to a reference 8YSZ powder. A modified Ni-8YSZ anode as well as a nickelate cathode were found to reach low polarization resistances of respectively 0.37 and less than 0.20 Ohm.cm² at 600°C. The progressive implementation of these materials in MSC has led to improved performances in tubular MSC, with an ASR of 1.56 Ohm.cm² at 600°C. Durability over 500h and 500 thermal cycles have been successfully achieved.

The cell manufacturing of Metal Supported Cells (MSC) for IT-SOFC application (typically 600 °C) requires to operate under non oxidizing conditions at high temperature (typically > 950 °C). The most sensitive layer appears to be the cathode one, usually a mixed ionic and electronic oxide. The behavior (TGA, XRD analyses, TECs) of the lanthanide nickelates Ln2NiO4+δ (Ln = La, Pr or Nd) is reported when sintered at high temperature, under low pO2, down to 10-4 atm. Electrochemical Impedance Spectroscopy measurements on Ln2NiO4+δ//GDC//YSZ half cells sintered either in air or under argon at various temperatures show polarization resistance values that meet the target requirements (< 0.20 W.cm² at 600 °C), especially for La2NiO4+ δ and Pr2NiO4+ δ. These results are discussed in terms of structural and microstructural features.

A cobalt-free perovskite oxide Bi 0.5 Sr 0.5 Fe 0.8 Cu 0.2 O 3− δ (BSFC) has been investigated as novel cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The BSFC cathode exhibits good thermal stability and chemical compatibility with Ce 0.9 Gd 0.1 O 1.95 (CGO) electrolyte below 950 °C. The average thermal expansion coefficient (TEC) of BSFC is 13.1 × 10 −6 K −1 within a temperature range of 50–800 °C in air, which is close to that of CGO electrolyte. Meanwhile, the polarization resistant values ( R P ) of BSFC cathode on CGO electrolyte are 0.13, 0.32 and 0.76 Ω cm 2 at 700, 650 and 600 °C, respectively; the lowest cathode overpotential is 37 mV at a current density of 125 mA cm −2 at 700 °C in air. The CGO electrolyte-supported single cell with BSFC cathode exhibits maximum power density of 290 mW cm −2 at 700 °C using dry H 2 as the fuel. The rate-limiting step for oxygen reduction reaction (ORR) on BSFC cathode is oxygen surface adsorption-dissociation process. The attractive electrochemical performance demonstrates that BSFC oxide is a promising cathode material for IT-SOFCs.

International audience; The effect of gadolinium-doped ceria (GDC) interlayer on the Pr0.8Sr0.2Fe0.7Ni0.3O3-δ (PSFN8273) cathode performance and stability in solid oxide fuel cell (SOFC) operating conditions is investigated. Two different symmetrical half-cells, with dense GDC electrolyte pellet (GDC/PSFN cell) and with GDC interlayer deposited on yttria stabilized zirconia pellet (YSZ) (YSZ/GDC/PSFN cell), are prepared and characterized by electrochemical impedance spectroscopy (EIS) as a function of temperature. The fitting of the data is carried out using an adapted Equivalent Circuit (EC). The polarization resistance (Rp) is higher for the YSZ/GDC/PSFN cell compared to GDC/PSFN cell. This increase is assigned to the interface microstructure. Then, the electrochemical properties of the half-cell with GDC interlayer are measured in three-electrode configuration under dc cathodic overpotential. In addition, the long-term stability is evaluated through an ageing test applying a current density of −123 mA.cm −2 for 1000 hours at 700 °C under air. PSFN8273 appears to be stable as cathode with a decrease in overpotential of about 6% in the first 200 hours and a subsequently stabilization. These results mean that even if the GDC interlayer affect the cathode performance (in terms of Rp) it did not influence its stability, making PSFN8273 a suitable material as cathode for SOFC application.

International audience; The electrochemical performance of Pr2NiMnO6 (PNMO)-xCe0.9Gd0.1O1.95 (CGO) (x = 0–40 wt%) composite oxides as intermediate-temperature solid oxide fuel cell (IT-SOFC) cathode materials are evaluated. The electrochemical impedance spectroscopy (EIS) analysis results identify two consecutive electrode processes on the composite cathode. Among the various composites, PNMO-30CGO cathode exhibits the best electrochemical performance with the minimum polarization resistance of 0.23 Ω cm2 and the maximum exchange current density of 75 mA cm−2 at 700 °C in air. These values are almost constant even after 30-h operation. The oxygen reduction reaction (ORR) mechanism studies prove that the major rate-determining step is the charge-transfer process. Introducing CGO significantly improves the charge-transfer process, by increasing the triple phase boundary (TPB) length and oxygen vacancy concentration in the composite cathode.

International audience; In the solid oxide fuel cell field, the gadolinium doped ceria (GDC) is widely used as interlayer between oxygen electrode and electrolyte materials, as for instance La2NiO4+δ (LNO) and 3 mol.% Y2O3-ZrO2 (TZ3Y), respectively. However, cation interdiffusion occurs between GDC and LNO/TZ3Y during their sintering steps at high temperature, which finally lowers the electrochemical performance of the cathode for the oxygen reduction reaction (ORR). In this paper, an alternative interlayer is proposed, the praseodymium doped ceria (PrDC with 30 at.% Pr). It is shown that reactivity occurs between PrDC and TZ3Y, but the compounds formed seem to favour the ORR. Besides, little reactivity is detected between LNO and PrDC. As a result, the total resistances, i.e. series and polarization resistance obtained with a LNO//PrDC//TZ3Y half-cell from 500 °C to 800 °C are much lower than those obtained with a LNO//GDC//TZ3Y half-cell, sintered in the same conditions. In addition, differences in the shape of the impedance diagrams are observed depending on the interlayer: this feature is discussed throughout the paper.

International audience

Composite electrodes of Pr2NiO4+δ and Gd-doped ceria (Ce0.8Gd0.2O1.90 so-called GDC) have been prepared starting from a Pr-Ni nitrate solution (2:1 stoichiometry ratio) that was infiltrated into a porous GDC backbone made by screen printing onto 3 % yttria-stabilized zirconia membrane (90 μm thick). The crystallization of the Pr2NiO4+δ powder was first studied by X-ray diffraction: it highly depends on the annealing atmosphere (air or N2) and the formation of this phase as infiltrate is more difficult than for the powder. The electrochemical study performed on symmetrical cells shows that the polarization resistance decreases when the annealing temperature of the infiltrate electrode decreases. The lowest R p value is obtained for an annealing at 900 °C, for 2 h in N2, the value being 0.075 Ω cm2 at 600 °C in air.

International audience; Nd1−xBaCo2O6−δ (N1−xBCO) is evaluated as cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The effects of Nd-deficiency on the crystal structure, thermal expansion behavior, electrical conductivity and electrochemical performance are studied. N1−xBCO oxides crystallize in the orthorhombic symmetry with Pmmm space group. A good chemical compatibility between N1−xBCO and CGO electrolyte is found at 1100 °C in air. Introducing Nd-deficiency promotes the formation of oxygen vacancy, and significantly improves the electrochemical performance of N1−xBCO cathodes. The lowest area specific resistance (ASR) value of 0.043 Ω cm2 is obtained on the N0.96BCO cathode at 700 °C in air. The rate limiting step for electrochemical oxygen reduction reaction (ORR) is charge transfer process at the interface. The power output of the electrolyte supported cell Ni-CGO/CGO/N0.96BCO reaches 0.6 W cm−2 at 700 °C.

In CeO2-based solid electrolytes, it has been shown that point defects are directly responsible for oxygen ionic conduction. The ionic conductivity is strongly affected by the anion vacancy concentration which is enhanced by doping with aliovalent cations. When rare earth sesquioxides such as La2O3, Gd2O3, Sm2O3, Y2O3 are added to CeO2, the dopant cation substitutes for the cerium ion, and oxygen vacancies are created for charge compensation. Incorporation of trivalent dopants into CeO2 at the Ce4+ sites can be depicted by the following defect reaction (expressed in Kröger-Vink notation)

The praseodymium nickelate oxide Pr2NiO4+δ, a mixed conducting oxide, was evaluated as cathode for Low Temperature Solid Oxide Fuel Cell at T = 873 K, using zirconia-type electrolytes. The electrochemical performance of the porous cathode has been improved by optimisation of its microstructure combined with the use of a doped ceria barrier layer in between the cathode and zirconia electrolyte. Both low polarization and ohmic resistances were obtained using Pr2NiO4+δ powders with a median particle size of 0.4 µm. These manufacturing conditions resulted in a cathode microstructure with well established connections between the cathode particles and good adhesion of the cathode on the electrolyte. Full-sized anode supported cells have been manufactured using the same process conditions and tested. The best results were obtained when using a dense Ce0.8Gd0.2O1.9 (20CGO) barrier layer. Moreover, we developed a new route for depositing ceria thin films: the supercritical fluid deposition (SFD) technique. Interestingly, we could evidence that the deposit of a dense interlayer of a few tens of nanometer contributes to the lowering of the polarization resistance, but also that this result can be achieved with undoped ceria, although this material is never used for SOFC because of its low ionic conductivity level.

In this study, La-Si metallic coatings were synthesized by Direct Current Magnetron Sputtering of lanthanum and silicon targets in pure argon atmosphere. After the deposition stage, the ceramic apatite-structure coatings were obtained by thermal oxidation in air. The structural and chemical features of these films have been assessed by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The electrical properties were determined by complex impedance spectroscopy in planar configuration. The films with a La/Si atomic ratio close to the apatite composition La9.33(SiO4)6O2 deposited on different substrates were initially amorphous. After thermal oxidation at 1173 K in air, the coating crystallised under the expected apatite structure. SEM observation revealed that the film compactness and thickness increased after thermal oxidation. The electrical measurements carried out under air as a function of temperature (1200 to 800 K) show only one contribution for the apatite layer on the Nyquist diagram. The electrical properties were controlled by the Arrhenius law with an activation energy (Ea = 0.7 eV) slightly lower than that of the literature data. The ionic conductivity is around 10-2 S.cm-1 at 1175K.

International audience; Three selected materials have been prepared and shaped as cathode of half cells using the proton-conducting electrolyte BaCe0.9Y0.1O3 − δ (BCY10): two perovskite compounds, Ba0.5Sr0.5Co0.8Fe0.2O3 − δ (BSCF) and La0.6Sr0.4Fe0.8Co0.2O3 − δ (LSFC), and the praseodymium nickelate Pr2NiO4 + δ (PRN) having the K2NiF4-type structure. The electrochemical properties of these compounds have been studied under zero current conditions (two-electrode cell) and under polarization (three-electrode cell). Their measured area-specific resistances were about 1-2 Ω cm2 at 600 °C. Under direct current polarization, it appears that the three compounds show almost similar values of current densities at 625 °C; however, at lower temperatures, BSCF appears to be the most efficient cathode material.

International audience; Solid state ionic devices based on high-temperature proton conductors can be used for various applications, especially in a new class of fuel cells, the Protonic Ceramic Fuel Cell (SOFC-H+). These systems are currently operating at intermediate temperatures (500–600 °C) and one of the major problems is the overpotential at the cathode side. In this context, various perovskite oxides AMO3 − δ (A = La, Ba, Sr; M = Mn; Fe, Co, Ni) and A2MO4-type compounds (A = La, Nd, Pr or Sr; M = Ni) have been investigated. Their properties under moist cathodic atmosphere have been studied. Actually, they are stable and exhibit high electrical conductivity (σ > 100 S cm−1) as well as good electrocatalytic properties towards oxygen reduction. The electrochemical properties of these oxides deposited on the protonic electrolyte BaCe0.9Y0.1O3 − δ have been studied and the Area Specific Resistances have been measured under air/H2O (3%) atmosphere. The obtained values at 600 °C, especially for Ba0.5Sr0.5Fe0.8Co0.2O3 − δ and Pr2NiO4 + δ show to be promising cathode materials for Protonic Ceramic Fuel Cell applications.

International audience; Neodymium nickelate, with composition Nd2NiO4+δ is integrated as oxygen electrode in a solid oxide electrolyte supported cell made of a TZ3Y electrolyte and a Ni-CGO hydrogen electrode. This cell is tested in both fuel cell (SOFC) and electrolysis (SOEC) mode and the reversible operation is proven, ASR values being slightly lower in electrolysis mode. Performances in SOEC mode are compared with a commercial cell based on the same electrolyte and cathode, but with lanthanum strontium manganite (LSM) as anode. For a voltage of 1.3 V, current densities of 0.40, 0.64 and 0.87 A cm−2 are measured at 750, 800 and 850 °C, respectively; they are much higher than the ones measured in the same conditions for the LSM-containing cell. Indeed, for a voltage of 1.3 V, current densities are respectively 1.7, 3 and 4.2 times higher for the Nd2NiO4+δ cell than for the LSM one at 850, 800 and 750 °C, respectively. Consequently, Nd2NiO4+δ can be considered as a good candidate for operating below 800 °C as oxygen electrode for high temperature steam electrolysis.

Two rare-earth nickelates, with compositions Nd2NiO4+δ and La2NiO4+δ have been investigated as oxygen electrodes. Their polarization resistance was determined on symmetrical half-cells and was found much lower than for classical Sr-doped LaMnO3 (LSM) perovskite. Then Nd2NiO4+δ was integrated in an electrolyte supported cell and tested in both fuel cell (SOFC) and electrolysis (SOEC) modes. The performances of this cell were higher than the one of a LSM-containing one. ASR values measured for this cell at 0.7 V were equal to 0.60 and 1.09 Ω.cm², at 850 and 750{degree sign}C, respectively. At 850{degree sign}C, this value is 1.7 times lower compared to the LSM-containing cell. At 750{degree sign}C it is 5.6 times lower. These results seem to show that nickelates are particularly suitable for a use below 800{degree sign}C. Similar conclusions were obtained in electrolysis mode.

Until now, most cathode materials used in high temperature ceramic solid electrolyte oxide cells (SEOC) are perovskite-type MEIC compounds, AMO3-δ, showing oxygen sub-stoichiometry. Recently, a new family of overstoichiometric oxides, formulated A2MO4+δ with A = La, Nd, Pr, Sr and M = Ni, Cu, has been investigated. Due to their basic properties (large D* and k coefficients, high electrical conductivity), the nickelate compounds have been especially used in various applications. Nd2NiO4 and Pr2NiO4 exhibit very promising electrochemical properties down to temperature as low as 600{degree sign}C, as ITSOFC cathodes as well as PCFC cathodes (they are stable under moist air (3 -10 % H2O). In addition, encouraging cell tests (SOFC and PCFC) have been performed with both nickelates. Furthermore, these materials have been also used as HTSE anodes and first results show excellent performances. Thus, it appears that these materials show an extremely high flexibility for being used as air electrode in very different conditions in terms of oxygen partial pressure or/and water content. This is explained on the basis of structural features of these materials and the great ability of these compounds for accommodating the oxygen non-stoichiometry.

International audience; The ability of solid oxide fuel cells (SOFC) to utilize commonly available fuels with high efficiency at 650–1000 8C promises an effective and early reduction in carbon dioxide emissions. Decreasing the operating temperature of SOFC is an important technical goal toward down-sizing, frequent operation stop, and the use of low-cost flexible metal interconnectors. Improvement of the cell efficiency is largely dependent on decreasing the polarization at the cathode, because the cathodic overvoltage for oxygen reduction is significantly larger than the other various internal cell resistances...

International audience; The promising SOFC cathode material Pr2NiO4.22 has been studied in situ under a pure oxygen atmosphere from 25 to 950 °C by high resolution synchrotron X-ray powder diffraction. At room temperature (RT) δ = 0.22(1), the average crystal structure turns out to be monoclinic. The subtle monoclinic distortion (γ = 90.066(1)° at RT), retained up to 460 °C, is interpreted in terms of specific tilt schemes of the NiO6 octahedra. It is also shown that Pr2NiO4.22 is incommensurately structurally modulated already at room temperature, in the same manner as the homologous cobaltate La2CoO4.14. The phase transition to the High Temperature Tetragonal (HTT) phase was completed at 480 °C without any evidence for the Low Temperature Orthorhombic (LTO) phase allowing clarifying the phase diagram of this K2NiF4-type ternary oxide. Moreover, it turns out that above 800 °C, the HTT phase transforms reversibly into two coexisting isomorphous tetragonal phases. The incommensurate modulation subsists up to 950 °C, although modified concomitantly with the two abovementioned phase transformations. In addition, the role of kinetics on the decomposition process is highlighted through thermo-gravimetric analyses

International audience; The development of highly active, inexpensive and clean catalysts for applications in the oxygen evolution reaction (OER) is very important for energy storage and conversion. In this study, a reduced graphene oxide–Co3O4 yolk-shell nanocage (rGO–Co3O4 YSNC) composite material is prepared through a facile precipitation reaction with subsequent calcination and hydrothermal treatment. A strong chemical interaction formed between Co3O4 YSNCs and r-GO nanosheets is vital to produce a well wrapped composite material. This specific composite structure combines the high conductivity of r-GO together with the promising catalytic properties of the highly porous Co3O4 YSNCs, therefore the enhanced OER activity and stability is realized. The Tafel slope, current density at an overpotential of 450 mV and the overpotential at 10.0 mA cm−2 for the rGO–Co3O4 YSNC composite electrode are 84.9 mV dec−1, 19.9 mA cm−2 and 410 mV, respectively. Moreover, the composite electrode exhibits 2.8% attenuation of the current density after the 500th cyclic voltammetry test. These results are comparable to the currently reported high-performance OER catalysts, which prove that the rGO–Co3O4 YSNC composite material is a potential catalyst for oxygen evolution reactions.

International audience; The present work is focused on the study of Pr4Ni3O10+δ as a new cathode material for Solid Oxide Fuel Cells (SOFCs). The structural study leads to an indexation in orthorhombic structure with Fmmm space group, this structure being thermally stable throughout the temperature range up to 1000 °C under air and oxygen. The variation of oxygen content (10+δ) as a function of temperature under different atmospheres show that Pr4Ni3O10+δ is always oxygen over-stoichiometric, which further suggests its MIEC properties. The polarization resistance (Rp) of Pr4Ni3O10+δ electrode is measured for GDC/co-sintered and two-step sintered half cells. The Rp for co-sintered sample is found to be 0.16 Ω cm2 at 600 °C under air, which is as low as the one of highest performing Pr2NiO4+δ nickelate (Rp = 0.15 Ω cm2 at 600 °C). Moreover, an anode supported (Ni-YSZ//YSZ) single cell including GDC//Pr4Ni3O10+δ co-sintered electrode shows a maximum power density of 1.60 W cm−2 at 800 °C and 0.68 W cm−2 at 700 °C. Here, the work is emphasized on the very close electrochemical performance of Pr4Ni3O10+δ compared to the one of Pr2NiO4+δ with higher chemical stability, which gives great interests to consider this material as a very interesting oxygen-electrode for SOFCs.

International audience; The Pr2CuO4 (PCO) submicrofiber precursors are prepared by electrospinning technique and the thermo-decomposition procedures are characterized by thermal gravity (TG), X-ray diffraction (XRD), Fourier transform infrared spectoscopy (FT-IR), and scanning electron microscopy (SEM), respectively. The fibrous PCO material was formed by sintering the precursors at 900 °C for 5 hrs. The highly porous PCO submicrofiber cathode forms good contact with the Ce0.9Gd0.1O1.95 (CGO) electrolyte after heat-treated at 900 °C for 2 hrs. The performance of PCO submicrofiber cathode is comparably studied with the powder counterpart at various temperatures. The porous microstructure of the submicrofiber cathode effectively increases the three-phase boundary (TPB), which promotes the surface oxygen diffusion and/or adsorption process on the cathode. The PCO submicrofiber cathode exhibits an area specific resistance (ASR) of 0.38 Ω cm2 at 700 °C in air, which is 30% less than the PCO powder cathode. The charge transfer process is the rate limiting step of the oxygen reduction reaction (ORR) on the submicrofiber cathode. The maximum power densities of the electrolyte-support single cell PCO|CGO|NiO-CGO reach 149 and 74.5 mW cm−2 at 800 and 700 °C, respectively. The preliminary results indicate that the PCO submicrofiber can be considered as potential cathode for intermediate temperature solid fuel cells (IT-SOFCs).

A new iron titanyl phosphate Fe0.50Ti2(PO4)3 was synthesized by both solid-state reaction and Cu2+–Fe2+ ion exchange method. The material was then characterized by X-ray diffraction, Mossbauer, magnetic susceptibility measurements and optical absorption. The crystal structure of the compound was refined, using X-ray powder diffraction data, by the Rietveld profile method; it crystallizes in the rhombohedral system, space group R 3 ¯ , with a=8.511(1) A and c=20.985(3) A, V=1316.45(3) A3 and Z=6. The structure, which is compared to that of Mn0.50Ti2(PO4)3 is built up from [TiO6] octahedra and [PO4] tetrahedra which are linked by corner sharing along the c-axis. Fe2+ cations are located in half of the antiprism MI sites and are orderly distributed with vacancies within the two possible positions of the MI sites of R 3 ¯ . These results were supported by the Mossbauer studies that showed the presence of one Fe2+ site in the high spin state (t2g4eg2). The Curie–Weiss-type behavior is observed in the magnetic susceptibility. Diffuse reflectance spectrum indicates the presence of octahedrally coordinated Fe2+ ions.

The room-temperature crystal structure of a new Cu(II) oxyphosphate—α Cu0.50IITiO(PO4)—was determined from X-ray single crystals diffraction data, in the monoclinic system, space group P21/c. The refinement from 5561 independent reflections lead to the following parameters: a=7.5612(4)A, b=7.0919(4)A, c=7.4874(4)A, β=122.25(1)°, Z=4, with the final R=0.0198, wR=0.0510. The structure of α Cu0.50IITiO(PO4) can be described as a TiOPO4 framework constituted by chains of tilted corner-sharing [TiO6] octahedra running parallel to the c-axis and cross linked by phosphate [PO4] tetrahedra, where one-half of octahedral cavities created are occupied by Cu atoms. Ti atoms are displaced from the center of octahedra units in alternating long (2.308 A) and short (1.722 A) Ti–O(1) bonds along chains. Such O(1) atoms not linked to P atoms justify the oxyphosphate formulation α Cu0.50TiO(PO4). The divalent cations Cu2+ occupy a Jahn–Teller distorted octahedron sharing two faces with two [TiO6] octahedra. EPR and optical measurements are in good agreement with structural data. The X-ray diffraction results are supported by Raman and infrared spectroscopy studies that confirmed the existence of the infinite chains –Ti–O–Ti–O–Ti–. α Cu0.50TiO(PO4) shows a Curie–Weiss paramagnetic behavior in the temperature range 4–80 K.

International audience; Double perovskite oxide Pr2NiMnO6 is evaluated as a potential cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The reactivity test indicates that no reaction occurs between Pr2NiMnO6 and CGO at 1200 °C in air. The thermal expansion coefficients (TEC) of Pr2NiMnO6 are 10.6 × 10−6 K−1 in air and 11.5 × 10−6 K−1 in nitrogen atmosphere within a temperature range of 100–800 °C. The electrochemical properties of Pr2NiMnO6 cathode are characterized by ac impedance and dc polarization methods, respectively. The lowest area specific resistance (ARS) is 0.38 Ω cm2 at 700 °C in air. The dependence of ASR with oxygen partial pressure indicates that the charge transfer process is the rate-limiting step for oxygen reduction reaction on Pr2NiMnO6 cathode.

Materials formulated Ln 2 − x − y y Ca x NiO 4 + δ (with ( i ) x = y = 0 for Ln = La, Pr, Nd, (ii) x ≠ 0 when y = 0 or y ≠ 0 when x = 0 for Ln = Nd) have been prepared and characterized using various techniques with respect to their mixed ionic/electronic conducting properties. These oxides exhibit high electronic conductivity (≈ 100 S cm − 1 at T = 700 °C) as well as high values of oxygen diffusion and surface exchange coefficients ( D * and k , determined using SIMS analysis of the 18 O isotope). The oxygen diffusion performances of Pr 2 NiO 4 + δ are the highest ones among those of the studied compounds. Interestingly, in the Nd-series they are slightly improved by the creation of Nd vacancies, while they are affected by the substitution of Nd by Ca.