Lanthanum Gallate Electrolyte Research Articles

Plasma Sprayed LSGM Electrolyte for Intermediate Temperature Solid Oxide Fuel Cells

A strontium-and-magnesium-doped lanthanum gallate (LSGM) electrolyte was processed into a thick film ranging from 100 - 550 μm using a plasma spray technique, followed by post heat-treatment at elevated temperatures (500 - 800°C). The processed LSGM electrolyte was characterized in terms of its (1) physical properties including phase purity, crystallinity, density, and (2) electrochemical properties, including open circuit voltage, ionic conductivity, and ac impedance. The electrochemical properties of the plasma sprayed LSGM were also compared with press-and-sintered LSGM pellets. The as-sprayed electrolyte exhibited a single LSGM phase in a mixture of amorphous and crystalline states. The amorphous phase can completely transform into a crystalline phase at temperatures up to 800°C as revealed by the XRD and impedance studies. The successful processing of LSGM using an industrial plasma spray technique offers a potential opportunity for fabrication of solid oxide fuel cells (SOFCs) for intermediate temperature applications (500 - 800°C).

Direct Methane Oxidation in Micro-Tubular SOFCs Using Doped LaGaO3 Electrolyte

A problem associated with the direct oxidation of hydrocarbon fuels such as methane in a solid oxide fuel cell (SOFC) has been the rapid deactivation of the anode as a result of carbon deposition. However, the use of doped-ceria in the SOFC anode can potentially overcome this problem. A micro-tubular SOFC using strontium- and magnesium doped lanthanum gallate (LSGM) of composition La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 2.8 as the electrolyte was developed and tested using a doped-ceria based anode and a cathode material of La 0.6 Sr 0.4 CoO 3 . A power density of 307 mW/cm 2 was achieved for a methaneloxygen fuel corresponding to a current density of 614 mA/cm 2 at 900°C. The procedures involved in the extrusion of micro-tubular lanthanum gallate (LaGaO 3 ) electrolyte tubes are also discussed in this paper. This study shows that achieving a commercial SOFC which could be operated at intermediate temperatures (650-800°C) and that could avoid the direct use of hydrogen as the fuel, is not an impractical task in the near future.

Lanthanum Gallate Electrolyte for Intermediate Temperature Operation

Lanthanum Gallate Electrolyte for Intermediate Temperature Operation

Development of Intermediate-Temperature SOFC Module Using Doped Lanthanum Gallate

Mitsubishi Materials Corporation (MMC) and the Kansai Electric Power Co., Inc. (KEPCO) are jointly developing intermediate temperature SOFCs that use doped lanthanum gallate electrolyte. The primary target of the collaboration is the development of modular SOFC systems for on-site power generation. Manufacturing technology of electrochemically active cells composed of (La,Sr)(Ga,Mg,Co)O 3 electrolyte, Ni-(Ce,Sm)O 2 anode and (Sm,Sr)CoO 3 cathode was established using tape-casting and screen-printing methods. Seal-less planar-type stack design was employed for manufacturing kilowatt-scale modules. The first generation module successfully provided the output power of 1 kW with thermal self-sustainability below 800°C. Maximum electrical efficiency obtained with this module was 43% [LHV] together with the corresponding fuel utilization of 78%. Dynamic performance tests demonstrated the capability of output power alteration from 0.6 to 1 kW while maintaining high electrical conversion efficiency. Further testing and modification of the module for methane fuel utilization are in progress.

Fabrication and Testing of a Doped Lanthanum Gallate Electrolyte Thin-Film Solid Oxide Fuel Cell

A supported lanthanum gallate (LSGM) electrolyte thin-film solid oxide fuel cell with Ni-YSZ cermet anode and strontium-doped lanthanum manganite (LSM)-yttria stabilized zirconia (YSZ) composite cathode was, for the first time, fabricated and tested. The cell was prepared by an unconventional approach, in which an LSGM thin film (about 15 μm thick) was first deposited on a porous substrate such as a porous YSZ disk by a wet process and sintered at a high temperature (above 1400°C). NiO was then incorporated into the porous substrate by a carefully controlled impregnation process and fired at a much lower temperature. In this way, the severe reaction between LSGM and NiO at a high temperature, which is required for the full densification of LSGM film, can be avoided. A strontium-doped (LSM)-YSZ composite cathode was screen printed on the surface of the LSGM film and then fired at 1250°C. The electrolyte resistances of the SOFC single cells fabricated by this approach are much lower compared to those of thick LSGM film supported cells. A maximum output power density of over at 800°C with as fuel and air as oxidant for a fabricated cell was achieved. © 2002 The Electrochemical Society. All rights reserved.

Preparation of Doped Lanthanum Gallate Electrolyte for SOFC by Pulsed Laser Deposition

AbstractIn this study, doped lanthanum gallate (LSGM with the composition La0.9Sr0.1Ga0.8Mg0.2O3-δ, LSGMC with the composition La0.8Sr0.2Ga0.8Mg0.15Co0.05O3-δ) films for an electrolyte of the solid oxide fuel cell (SOFC) were prepared by pulsed laser deposition (PLD) technique. In the vacuum chamber, LSGM or LSGMC targets were set on the rotating target holder. A KrF excimer laser was introduced into the chamber at an incident angle of about 45 degree. The doped LaGaO3 film was deposited onto NiO substrates without heating in argon ambient gas. The NiO substrate can be used directly as an electrode in the fabrication of the SOFC. The deposited LSGM films were characterized by X-ray diffraction (XRD), secondary ion mass spectroscopy (SIMS) and scanning electron microscopy (SEM). As-deposited films were amorphous. After post annealing at 1273K for 6-10 hours, crystalline LaGaO3 was obtained. Films with thickness greater than several 10 μm showed an uniform and dense morphology. No gas leakage was found using thick films, which is an important characteristic for an electrolyte in fuel cells. The composition of the deposited films was slightly different to that of the target.

Interactions of a La 0.9Sr 0.1Ga 0.8Mg 0.2O 3− δ electrolyte with Fe 2O 3, Co 2O 3 and NiO anode materials

In this study, the interactions of a Sr- and Mg-doped lanthanum gallate (LSGM with composition La 0.9Sr 0.1Ga 0.8Mg 0.2O 3− δ ) electrolyte with Fe 2O 3, Co 2O 3 and NiO as the anode starting materials were investigated. It was found that the order of reactivity of the LSGM with the three oxides was Co 2O 3>NiO>Fe 2O 3, and La-containing oxides were detected in these binary powder mixtures after firing. The anode performance was greatly influenced by the interaction. The Fe 2O 3–LSGM anode, mixed with 40 vol.% LSGM powder and sintered at 1150°C, exhibited the highest initial performance in comparison with NiO–LSGM and Co 2O 3–LSGM anodes. It seems that Fe 2O 3 is a possible anode starting material for a LSGM-based solid oxide fuel cell.

Intermediate Temperature Solid Oxide Fuel Cells with Doped Lanthanum Gallate Electrolyte, La(Sr)CoO3 Cathode, and Ni-SDC Cermet Anode

Intermediate Temperature Solid Oxide Fuel Cells with Doped Lanthanum Gallate Electrolyte, La(Sr)CoO3 Cathode, and Ni-SDC Cermet Anode

00/03381 High performance electrodes for reduced temperature solid oxide fuel cells with doped lanthanum gallate electrolyte I. NiSDC cermet an

00/03381 High performance electrodes for reduced temperature solid oxide fuel cells with doped lanthanum gallate electrolyte I. NiSDC cermet an

00/03382 High-performance electrodes for reduced temperature solid oxide fuel cells with doped lanthanum gallate electrolyte II. La(Sr)CoO 3 cathode

00/03382 High-performance electrodes for reduced temperature solid oxide fuel cells with doped lanthanum gallate electrolyte II. La(Sr)CoO 3 cathode

Chemical compatibility of alternative perovskite oxide SOFC cathodes with doped lanthanum gallate solid electrolyte

This paper reports on the investigations of the chemical compatibility between SOFC cathode materials with compositions Pr 0.8Sr 0.2Co 0.2Mn 0.8O 3− δ , Pr 0.8Sr 0.2Co 0.2Fe 0.8O 3− δ , Pr 0.8Sr 0.2Co 0.3Mn 0.7O 3− δ and Pr 0.75Sr 0.2Co 0.2Mn 0.8O 3− δ and the electrolyte materials with compositions La 0.8Sr 0.2Ga 0.9Mg 0.1O 3− δ , and La 0.9Sr 0.1Ga 0.8Mg 0.2O 3− δ . The lanthanum gallate electrolyte with 20 mol.% Sr contained two additional phases, namely, LaSrGa 3O 7 and LaSrGaO 4, while that with 10 mol.% Sr was formed in nearly single phase. Two types of experiments were performed: (a) reactivity experiments of powder mixtures and (b) diffusion experiments in cathode/electrolyte double-layer pellets. No reaction products were detected by XRD. High Co diffusion into the electrolyte was identified with SEM/EDX in all diffusion experiments examined. The transition metals diffuse in the order Mn<Fe<Co. La, Pr and Ga show a smaller tendency for diffusion. The diffusion of transition metal cations into the electrolyte La 0.8Sr 0.2Ga 0.9Mg 0.1O 3− δ caused the destabilisation and disappearance of the second phases in the interdiffusion zone. In the case of the A-site deficient cathode, the formation of LaSrGa 3O 7 second phase was identified on the electrolyte side, near the interdiffusion zone.

Interface reactions in the NiO–SDC–LSGM system

The reactivity of NiO–SDC (samaria-doped ceria) anode material with a Sr- and Mg-doped lanthanum gallate (LSGM) electrolyte was studied by X-ray diffraction (XRD) and electrical measurements. It was found that a LaNiO 3-based compound in hexagonal structure formed in binary powder mixtures of NiO and LSGM after firing at 1150°C. Reaction between SDC and LSGM was also observed. Several SDC peaks merged with the adjacent LSGM peaks during firing, and a SrLaGa 3O 7 compound was identified as a reaction product. Reaction between LSGM and SDC could cause more than 50% loss in the ionic conductivity of LSGM–SDC electrolytes sintered at 1350°C. The measured conductivity of an LSGM electrolyte with a NiO–LSGM anode prepared at 1350°C was extremely low, indicating that the LaNiO 3-based new phase is highly insulating. The reaction between NiO and SDC was not so obvious in comparison with NiO–LSGM and SDC–LSGM binary mixtures.

High-performance electrodes for reduced temperature solid oxide fuel cells with doped lanthanum gallate electrolyte: II. La(Sr)CoO 3 cathode

The reduced temperature solid oxide fuel cell (SOFC) with 0.5 mm thick La 0.9Sr 0.1Ga 0.8Mg 0.2O 3− α (LSGM) electrolyte, La 0.6Sr 0.4CoO 3− δ (LSCo) cathode, and Ni-(CeO 2) 0.8(SmO 1.5) 0.2 (SDC) cermet anode showed an excellent initial performance, and high maximum power density, 0.47 W/cm 2, at 800°C. The results were comparable to those for the conventional SOFC with yttria-stabilized zirconia (YSZ) electrolyte, La(Sr)MnO 3-YSZ cathode and Ni–YSZ cermet anode at 1000°C. Using an LSCo powder prepared by spray pyrolysis, and selecting appropriate sintering temperatures, the lowest cathodic polarization of about 25 mV at 300 mA/cm 2 was measured for a cathode prepared by sintering at 1000°C. Life time cell test results, however, showed that the polarization of the LSCo cathode increased with operating time. From EPMA results, this behavior was considered to be related to the interdiffusion of the elements at the cathode/electrolyte interface. Calcination of LSCo powder could be a possible way to suppress this interdiffusion at the interface.

High performance electrodes for reduced temperature solid oxide fuel cells with doped lanthanum gallate electrolyte: I. Ni–SDC cermet anode

A Ni–samaria-doped ceria (SDC) cermet was selected as the anode material for reduced temperature (800°C) solid oxide fuel cells. The NiO–SDC composite powder, synthesized by spray pyrolysis, was employed as the starting anode powder in this study. The influence of Ni content in Ni–SDC cermets on the electrode performance was investigated in order to create the most suitable microstructures. It was found that anodic polarization was strongly influenced by the Ni content in Ni–SDC cermets. The best results were obtained for anode cermets with Ni content of around 50 vol.%; anodic polarization was about 30 mV at a current density of 300 mA/cm 2. This high performance seems to be attributable to the microstructure, in which Ni grains form a skeleton with well-connected SDC grains finely distributed over the Ni grains surfaces; such microstructure was also conducive to high stability of the anode.

Ni-SDC cermet anode for medium-temperature solid oxide fuel cell with lanthanum gallate electrolyte

The polarization properties and microstructure of Ni-SDC (samaria-doped ceria) cermet anodes prepared from spray pyrolysis (SP) composite powder, and element interface diffusion between the anode and a La 0.9Sr 0.1Ga 0.8Mg 0.2O 3− δ (LSGM) electrolyte are investigated as a function of anode sintering temperature. The anode sintered at 1250°C displays minimum anode polarization (with anode ohmic loss), while the anode prepared at 1300°C has the best electrochemical overpotential, viz., 27 mV at 300 mA cm −2 operating at 800°C. The anode ohmic loss gradually increases with increase in the sintering temperature at levels below 1300°C, and sharply increases at 1350°C. Electron micrographs show a clear grain growth at sintering temperatures higher than 1300°C. The anode microstructure appears to be optimized at 1300°C, in which nickel particles form a network with well-connected SDC particles finely distributed over the surfaces of the nickel particles. The anode sintered at 1350°C has severe grain growth and an apparent interface diffusion of nickel from the anode to the electrolyte. The nickel interface diffusion is assumed to be the main reason for the increment in ohmic loss, and the resulting loss in anode performance. The findings suggest that sintering Ni-SDC composite powder near 1250°C is the best method to prepare the anode on a LSGM electrolyte.

Solid Oxide Fuel Cells with Doped Lanthanum Gallate Electrolyte and LaSrCoO3 Cathode, and Ni‐Samaria‐Doped Ceria Cermet Anode

The electrode performance of a single solid‐fuel cell (SOFC) was evaluated using a 500 μm thick (LSGM) as the electrolyte membrane. A doped lanthanum cobaltite, was selected as the cathode material, and a samaria‐doped ceria‐NiO composite powder was used as the anode material. The spray‐pyrolysis method was applied for synthesis of the starting powders of the cathode and anode. In this study, different microstructures of the cathode were obtained by varying the sintering temperature from 950 to 1200°C. High power density (the maximum power density of the cell was about , which is 95% of the theoretical value) of the solid oxide fuel cell at 800°C was achieved. The cell performance showed that, with a proper choice of electrode materials with optimized microstructure and LSGM as the electrolyte, a SOFC operating at temperatures is a realistic goal. © 1999 The Electrochemical Society. All rights reserved.

Fuel cells with doped lanthanum gallate electrolyte

Single cells with doped lanthanum gallate electrolyte material were constructed and tested from 600 to 800°C. Both ceria and the electrolyte material were mixed with NiO powder respectively to form composite anodes. Doped lanthanum cobaltite was used exclusively as the cathode material. While high power density from the solid oxide fuel cells at 800°C was achieved. our results clearly indicate that anode overpotential is the dominant factor in the power loss of the cells. Better anode materials and anode processing methods need to be found to fully utilize the high ionic conductivity of the doped lanthanum galiate and achieve higher power density at 800°C from solid oxide fuel cells.