微波辅助PVP溶液聚合法制备LSGM电解质粉末

采用PVP溶液聚合法成功制备出了高纯度La0.8Sr0.2Ga0.83Mg0.17O2.815粉末;研究了不同含量聚合载体(PVP)对试验结果的影响规律,找到了能保证金属离子在聚合网状结构中均匀分布并防止偏析的最佳的PVP含量,证明了PVP可以作为一种制备LSGM粉末的更为有效的载体;探索了所制备产物在不同温度下的煅烧行为.与传统的Pechini法相比,本实验所需有机物聚合载体(PVP)的量更少.而微波具有更高的加热速率,加热时反应体系中不会存在温度梯度,使得反应更加均匀,制备的粉末杂质更少,压片烧结后其晶粒尺寸也更小(2～3 μm).     

Studies on electrical properties of La0.8Sr0.2Ga0.8Mg0.2O2.80 (LSGM) and LSGM-SrSn1−xFexO3 (x = 0.8; 0.9) composites and their chemical reactivity

We report the electrical conductivity properties of solid-state synthesized perovskite-like La_0.8Sr_0.2Ga_0.8Mg_0.2O_2.80 (LSGM) and LSGM-SrSn_1−xFe_xO₃ (x = 0.8; 0.9) composites. LSGM exhibits both bulk and grain-boundary contribution in the ac impedance plots. The grain-boundary conductivity (σ_gb) is slightly (≤half-order of magnitude) higher than that of the bulk oxide ion conductivity (σ_bulk). Powder XRD study reveals that no chemical reaction occurs between LSGM and SrSn_1−xFe_xO₃ (1:1 wt.%) at 1000 °C (48 h) and forms a single-phase perovskite-like compound at 1300 °C (48 h) in air, while in hydrogen atmosphere, at 800 °C for 48 h, a growth of LaSrGaO₄ and LaSrGa₃O₇ impurity phases and formation of metallic Fe was observed. The LSGM-SrSn_1−xFe_xO₃ (x = 0.8; 0.9) composites show a single or part of semicircle in air at low-temperature regime. The electrical conductivity of the composites were found to be much higher compared to pure LSGM and lower about an order of magnitude than those of pure Sn-doped SrFeO₃ perovskite.     

Electrochemical effects of cobalt doping on (La,Sr)(Ga,Mg)O3−δ electrolyte prepared by aerosol deposition

(La,Sr)(Ga,Mg)O_3−δ and (La,Sr)(Ga,Mg,Co)O_3−δ electrolytes were aerosol deposited on conventionally sintered NiO-GDC anode substrates at room temperature to minimize reactions between them. Composite cathodes comprising (La,Sr)(Co,Fe)O_3−δ and polyvinylidene fluoride were similarly deposited at room temperature. Both electrolytes and cathode maintained good adhesion. Cobalt in the electrolyte reduced open cell voltage (∼0.8 V vs. ∼1.1 V) probably due to the decrease of ionic transfer number, and increased maximum power density (∼0.8 W/cm² vs. ∼0.5 W/cm² at 650 °C) by increasing ionic conductivity.     

Preparation and characterization of La0.9Sr0.1Ga0.8Mg0.2O3−δ thin film electrolyte deposited by RF magnetron sputtering on the porous anode support for IT-SOFC

Thin films of solid electrolyte La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ (LSGM) were deposited by RF magnetron sputtering onto porous La_0.7Sr_0.3Cr_0.5Mn_0.5O_3−δ (LSCM) anode substrates. The effects of substrate temperature, sputtering power density and sputtering Ar gas pressure on the LSGM thin film density, flatness and morphology were systematically investigated. RF sputtering power density of 7.8 W cm⁻², substrate temperature of 300 °C and sputtering Ar gas pressure of 5 Pa are identified as the best technical parameters. In addition, a three-electrode half cell configuration was selected to investigate the electrochemical performance of the thin film. The LSGM film deposited at optimum conditions exhibited a lower area specific ohmic resistance of 0.68 Ω cm⁻² at 800 °C, showing that the practicability of RF magnetron sputtering method to fabricate LSGM electrolyte thin film on porous LSCM anode substrates.     

Oxygen ion transference number of doped lanthanum gallate

The transference numbers for oxygen ion (t_O) in several LaGaO₃-based materials are determined from oxygen concentration cells using the materials as the electrolyte, including La_0.8Sr_0.2Ga_0.8Mg_0.2O_3−δ (LSGM8282), La_0.8Sr_0.2Ga_0.8Mg_0.15Co_0.05O_3−δ (LSGMC5) and La_0.8Sr_0.2Ga_0.8Mg_0.115Co_0.085O_3−δ (LSGMC8.5). Analysis indicates that the accuracy in determination of oxygen ion transference number depends on the electrode polarization resistances of the concentration cell as well as the transport properties of the materials studied. For example, the ratio of open cell voltage to Nernst potential is a good approximation to the ionic transference number for LSGM8282. However, this approximation is no longer adequate for LSGMC5 and LSGMC8.5; the effect of electrode polarization resistances must be taken into consideration in estimation of the ionic transference numbers. In particular, the ionic transference number for LSGMC5 is as high as 0.99, suggesting that it is a promising electrolyte material for low-temperature solid-state electrochemical applications.     

LSGM固体电解质薄膜制备的研究进展

Sr和Mg掺杂的稀土钙钛矿型氧化物LaGaO3(LSGM)是具有广泛应用前景的固体电解质材料.本文综述了LSGM薄膜制备的主要方法,讨论了各种方法的优缺点,最后对LSGM薄膜制备方法的进一步研究方向进行了展望.     

Improved power generation performance of solid oxide fuel cells using doped LaGaO3 electrolyte films prepared by screen printing method II. Optimization of Ni-Ce0.8Sm0.2O1.9 cermet anode support

A Ni and Sm-doped ceria (Ce_0.8Sm_0.2O_1.9, SDC) cermet anode as a porous support of doped LaGaO₃ film prepared by a wet coating and co-firing process was investigated. Different preparation methods and compositions were used to improve the power density of intermediate temperature solid oxide fuel cells. NiO-SDC precursor powder with fine particles and a porous microstructure with high surface area was synthesized by a modified impregnation method and compared with that synthesized by a ball milling method. In addition, an open circuit voltage, which is almost equal to the theoretical value of 1.1 V, and maximum power densities of 835, 277, and 67 mW cm⁻² at 700, 600, and 500 °C, respectively, were achieved on a single cell supported by a 75 wt% Ni-SDC cermet anode when a 60 μm thick Sr- and Mg-doped lanthanum gallate (LSGM) electrolyte was used. The improved power density was explained by the enlarged reaction area for the anode as a result of the low polarization resistance of the anode by high porosity and uniform distribution of Ni and SDC particles. Although a small amount of Ni diffused to the interface between the La-doped ceria (LDC) buffer layer and the LSGM electrolyte film, an adverse reaction that deteriorates cell performance seemed to be suppressed, and thus, reasonably high power density was achieved on the cell using the LSGM film prepared by the screen printing method with optimization of the anode substrate structure and composition.     

A High Power Density Intermediate‐Temperature Solid Oxide Fuel Cell with Thin (La0.9Sr0.1)0.98(Ga0.8Mg0.2)O3‐δ Electrolyte and Nano‐Scale Anode

Solid oxide fuel cells (SOFCs) with thin (La_0.9Sr_0.1)_0.98Ga_0.8Mg_0.2O_3‐δ (LSGM) electrolytes are primary candidates for achieving high (> 1 W cm^‐2) power density at intermediate (< 650 °C) temperatures. Although high power density LSGM‐electrolyte SOFCs have been reported, it is still necessary to develop a fabrication process suitable for large‐scale manufacturing and to minimize the amount of LSGM used. Here we show that SOFCs made with a novel processing method and a Sr_0.8La_0.2TiO_{3‐ α} (SLT) oxide support can achieve high power density at intermediate temperature. The SLT support is advantageous, especially compared to LSGM supports, because of its low materials cost, electronic conductivity, and good mechanical strength. The novel process is to first co‐fire the ceramic layers – porous SLT support, porous LSGM layer, and dense LSGM layer – followed by infiltration of nano‐scale Ni into the porous layers. Low polarization resistance of 0.188 Ωcm² was achieved at 650 °C for a cell with an optimized anode functional layer (AFL) and an (La,Sr)(Fe,Co)O₃ cathode. Maximum power density reached 1.12 W cm^?2 at 650 °C, limited primarily by cathode polarization and ohmic resistances, so there is considerable potential to further improve the power density.     

Synthesis of pure powder of La0.9Sr0.1Ga0.8Mg0.2O2.825 by microwave-induced solution combustion method

Solid oxide fuel cell(SOFC)has recently captured great con-cern for its characteristics such as environment-friendly,high effi-ciency,good fuel adaptability andlownoise·Sr and Mg doped La-GaO3(LSGM)as electrolytesin SOFCexhibits higher oxygenionicconduct…     

Co-precipitation in aqueous medium of La0.8Sr0.2Ga0.8Mg0.2O3−δ via inorganic precursors

A simple and inexpensive co-precipitation route in aqueous medium is proposed to prepare La_0.8Sr_0.2Ga_0.8Mg₀₂O_3−δ ionic conductor (LSGM). Different synthetic procedures and operating parameters (i.e. nature and amount of the precipitating agents, HNO₃ addition and temperature) have been evaluated in order to underline their influence on the composition and microstructure of the final phase. Intermediate and final products were characterized by Thermal-Gravimetry, IR-spectroscopy, X-ray Powder Diffraction, Rietveld analysis and Scanning Electron Microscopy. The electrical properties were measured by Impedance Spectroscopy in the temperature range 250-800 °C. Slight variations of the synthetic procedure (such as precipitating agent amount or no HNO₃ addition) have a considerable and detrimental effect on the ions losses and the subsequent achievement of the final phase. The use NH₄OH as an alternative precipitating agent is dramatically disadvantageous. Ions losses during precipitation must be controlled (i) to avoid understoichiometry in the LSGM phase and (ii) to prevent the formation of large amounts of secondary phases. In fact, both affect the total electrical conductivity.The use of large excess of (NH₄)₂CO₃ precipitating agent and the addition of HNO₃ lead to the best material characterized by a rhombohedral structure, small amount of side phases, a relative density of 98% and a total conductivity of 6.44 × 10⁻² S cm⁻¹ at 800 °C and 1.13 × 10⁻² S cm⁻¹ at 600 °C.