Papers by Keyword: LSGM

Abstract: The LSGM-carbonate composite electrolyte is a new type of medium and low temperature SOFC electrolyte material, which has great application potential. In this paper, the molten salt infiltration method was used to prepare the LSGM-carbonate composite electrolyte. The results of SEM test proved that the molten salt infiltration method was more appropriate in preparing the LSGM-carbonate composite electrolyte comparing with direct mixing method. The influence of the type and content of pore forming agent was investigated. The result showed that the polymethyl methacrylate (PMMA) had an excellent pore forming performance and could create interconnected pore structures successfully in LSGM matrix. The XRD result indicated that the LSGM-carbonate composite electrolyte showed almost a single LSGM phase and the carbonate remained glass state. Four terminal method was used to measure the conductivity. The result showed that the conductivity of the LSGM-carbonate composite electrolytes was increased by one order of magnitude compared with pure LSGM. The conductivity of LSGM-carbonate composite electrolytes increased firstly and then decreased with the increasing of PMMA. The LSGM-carbonate composite electrolyte prepared by 25 wt.% PMMA addition has the highest conductivity during the whole range of test temperature and reached 0.3 S.cm^-1 at 600°C.

Abstract: The surface modification of Gd doped ceria (GDC) and Sr-and Mg-codoped lanthanum gallate (LSGM) powders with cationic and anionic polyelectrolytes, Poly (diallyldimethylammonium chloride) (PDDA) and poly (2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS), respevtively, was performed by the Layer by Layer (LbL) adsorption method to improve the surface-charging uniformity. The tri-layer of GDC/LSGM/GDC was deposited on a polypyrrole coated porous NiO-YSZ substrate by sequential EPD using the ethanol-based suspensions of the surface-modified powders. The topcoating of hydroxyl-propyl cellulose (HPC) on the deposited layers was conducted to control the drying rate with suppressing the cracking and peeling-off of the deposits. The advantage of the use of those polymers for the EPD process including the drying technique was demonstrated.

Abstract: Dense micrometric La_0.8Sr_0.2Ga_0.8Mg_0.2O_3-δ (LSGM) films were deposited by spin-coating on porous LSGM scaffolds characterized by an homogeneous pore structure. Porous anodes were infiltrated with aqueous nickel nitrate solutions, dried and fired at 700 °C. Homogeneous metal coating with proper interconnections was observed by SEM, chemical stability was confirmed by XRD. Fuel cell tests and electrochemical impedance spectroscopy (EIS) were performed and discussed.

Abstract: La_0.9Sr_0.1Ga_0.8Mg_0.2O_2.85 (LSGM) electrolyte films were successfully prepared by slurry spin coating method on porous La_0.7Sr_0.3Cr_0.5Mn_0.5O_2.75 (LSCM) anode substrates. Ethyl celluloses content, coating cycles for slurry spin coating on the fabrication LSGM electrolyte films were investigated. The compatibility between LSGM and LSCM powders, microstructures and electricity conductivity of fabricated LSGM films were examined using XRD, SEM and electrochemical workstation. The film with good apparent morphology and electrical conductivity were obtained when the operating parameters were setted as the content of ethyl cellulose 10wt%, and the coating cycles 5.

Abstract: . La_0.8Sr_0.2Ga_0.8Mg_0.2O_2.8 (LSGM) acts as a promising electrolyte material for solid oxide fuel cell (SOFC) at intermediate temperature although its single phase synthesis is comparably difficult. However, phase purity is influenced by the amount and type of the transition metals doped and with the addition of transition metals both bulk and grain boundary conductivities are increased. In this work, Co is doped at Ga site of LSGM by Pechini method. The powders are then calcined, sintered and subsequently characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermo-mechanical (TMA), nanoindentation test and impedance analysis. As observed from XRD single phase La_0.8Sr_0.2Ga_0.8Mg_0.15 Co_0.05O_2.8 (LSGMC) is found at 1400°C and getting its single phase is easier than synthesizing single phase LSGM. As found from Rietveld analysis, the synthesized LSGMC is having orthorhombic crystal structure with Pbnm space group. TEM images show the spherical particles with size ~35 nm. Density of the sintered pellet as measured by Archimedes principle is found to be 98% at 1400°C, 8h. Thermal expansion co-efficient of the sintered pellet is found to be 12.2 ×10^-6/°C, which is nearly same as of LSGM and nearly matches with other SOFC components. Hardness and Youngs modulus of the material as found from the Nanoindentation test are found as 13.14 ±0.9 GPa and 204.5±5.7 GPa respectively, which are suitable for SOFC application. The diffused semicircle observed in Nyquist plot simulated as (RQ)(RQ) circuit and the ionic conductivity is found to be higher than LSGM at equivalent temperature.

Abstract: High-quality La_0.84Sr_0.16Ga_0.26Mg_0.74O_3-δ (LSGM) epitaxial thin films were successfully grown on (100)-SrTiO₃ (STO) substrates at a temperature of 800 °C by a pulsed laser deposition (PLD) method with KrF excimer laser pulses at an ozone pressure of 1.3 × 10³ Pa. X-ray diffraction rocking curve measurements showed that the LSGM films had a full-width at half-maximum (FWHM) value of 0.11 °for out-of-plane 002 reflection, which was smaller than that reported for LaGaO₃ films grown by atomic layer deposition methods (0.18 ^o). The reciprocal spaces mapping of 103 refraction showed that the LSGM films had a slightly larger lattice parameter a (out-of-plane) of 0.393 nm than a_// (in-plane) of 0.391 nm.

Abstract: In order to discuss the growth mechanism of LSGM films, La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM) thin films electrolytes were fabricated on Si substrates by RF magnetron sputtering. The atomic force microscope (AFM) and X-ray diffraction analyzer (XRD) were used to analyze film surface morphology and phase components. The results show that LSGM films are grown with island structure. When the deposition time increases to 30min, the preferred growth orientations appears, which is (112) crystal face. The longer deposition time is, and the rougher the surface possesses.

Abstract: In the present work a modified polymeric precursor route is applied for the preparation of La1-xSrxGa0.8Mg0.2O3-δ (x=0.1, 0.2, 0.3). Citric acid and ethylene glycol are used as chelating and complexing agents respectively and microwave heating is used for the preparation of the precursors. The sintering reactions are recorded using TG/DTG measurements, while XRD, FTIR and SEM are used for the characterization of the intermediate and final products. As it is concluded, pure La0.9Sr0.1Ga0.8Mg0.2O3 can be prepared after sintering at 1300 °C for 6h. As the doping level of Sr increases, the formation of single phase perovskite is hindered. La0.8Sr0.2Ga0.8Mg0.2O3 contains minor amounts of SrLaGa3O7, while single-phase La0.7Sr0.3Ga0.8Mg0.2O3 can not be prepared at all. In all cases, the intermediate products at lower temperatures are mainly SrLaGa3O7, SrLaGaO4, La4Ga2O7 and La carbonates.

Abstract: Single phase La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM9182) was synthesized by a polymeric precursor route. The XRD pattern after calcination at 1300 °C for 6h indicates the formation of the perovskite without the presence of secondary phases. XRD, FTIR and TG-DTG measurements were used to examine the powder precursor as well as the intermediate and final products. SEM images indicated the small grain size of the final product. The conductivity of the sintered sample was examined by means of a.c. impedance spectroscopy and was found to be 9.10-2 S/cm at 800 °C similar to the typical value of LSGM materials.

Abstract: The production of La0.95Sr0.05Ga0.90Mg0.10O3-δ powders was achieved at room temperature by a mechanosynthesis route in a high energy planetary ball mill starting from a mixture of lanthanum, strontium, gallium and magnesium oxides. The milling was carried out in nylon containers, using zirconia balls and a balls:powder mass ratio of 10:1. The planetary rotation was kept constant at 650 rotations per minute (rpm), and the container at 1300 rpm, in the opposite direction. The formation of the perovskite phase was detected from the early milling stages and nearly completed after milling for 360 min, as shown by powder X-ray diffraction. Transmission electron microscopy results revealed that powders consist of agglomerates of homogeneous, crystalline particles with an average equivalent diameter of about 16-17 nm, in excellent agreement with average crystallite size estimates obtained from X-ray diffraction.