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1.
Reactions between Strontium-Substituted Lanthanum Manganite and Yttria-Stabilized Zirconia: II, Diffusion Couples 总被引:1,自引:0,他引:1
Kjersti Kleveland Mari-Ann Einarsrud Christian R. Schmidt Senem Shamsili Sonia Faaland Kjell Wiik Tor Grande 《Journal of the American Ceramic Society》1999,82(3):729-734
Formation of secondary phases and diffusion of cations in diffusion couples of yttria-stabilized zirconia and lanthanum manganite substituted with 0 to 60 mol% strontium have been studied by scanning electron microscopy and energy dispersive X-ray spectroscopy. Only the primary phases were observed after 120 h at 1200°C, while formation of secondary phases was identified already after 1 h heat treatment at 1350°C. The phase composition of the reaction layer altered from La2 Zr2 O7 to SrZrO3 at increasing Sr content in La x Sr1- x MnO3 . The thickness of the reaction layer was increasing with heat treatment time. In diffusion couples of La0.4 Sr0.6 MnO3 formation of manganese oxide was observed in the perovskite layer after 1 h heat treatment at 1350°C, while isolated grains of SrZrO3 relatively deep inside the zirconia were observed after longer heat treatment time. Diffusion of Mn into zirconia was observed preferenced along grain boundaries in the early stage of the interface reaction. 相似文献
2.
Chih-Chung T. Yang Wen-Cheng J. Wei reas Roosen 《Journal of the American Ceramic Society》2004,87(6):1110-1116
The reaction kinetics and mechanisms between 8 mol% yttria-stabilized zirconia (YSZ) and 30 mol% Sr-doped lanthanum manganite (La0.65 Sr0.30 MnO3 , LSM) with A-site deficiency for the application of planar solid oxide fuel cells (SOFCs) were investigated. The LSM/YSZ green tapes were cofired from 1200° to 1400°C for 1 to 48 h and then annealed at 1000°C for up to 1000 h. The results showed that the diffusion of manganese cations first caused the amorphization of YSZ, and then the formation of small La2 Zr2 O7 (LZ) or SrZrO3 (SZ) crystals if treated for a longer time at 1400°C. The ambipolar diffusion of the Mn–O pair, transported through the migration of oxygen vacancy, plays an important role in the formation of secondary phases. The diffusion of LSM to YSZ and substitution of Mn for Zr both result in the enhanced concentration of oxygen vacancy, leading to the formation of a void-free zone (VFZ). No additional reaction products in annealed LSM/YSZ specimens, treated at 1000°C for 1000 h, were detected. The interfacial reactions, detailed reaction kinetics, and mechanisms are reported. 相似文献
3.
Chemical Compatibility between Strontium-Doped Lanthanum Manganite and Yttria-Stabilized Zirconia 总被引:1,自引:0,他引:1
Guido Stochniol Emmanuel Syskakis Aristides Naoumidis 《Journal of the American Ceramic Society》1995,78(4):929-932
Equimolar powder mixtures and multilayer pellets of single-phase Sr-doped lanthanum manganite perovskite materials Lay-x Srx MnO3 with La content y = 1 and 0.95 and Sr content 0 ≤ x ≤ 0.5 were annealed in air with 8 mol% Y2 O3 -ZrO2 at 1470 K, up to 400 h and at 1670 K. up to 200 h. X-ray diffraction and electron probe microanalysis confirmed the formation of La2 Zr2 O7 or SrZrO3 depending on the composition of the perovskites. No reaction products could be detected for La0.95-x Sr x MnO3 with 0.2 ≤ x ≤ 0.4 after annealing for 400 h at 1470 K, and for the perovskite La0.65 Sr0.3 MnO3 even after annealing for 200 h at 1670 K. The results demonstrate the improved chemical compatibility of La-deficient perovskites against reaction with zirconia and can provide a basis for the selection of a sufficiently chemically stable material for the air electrode of solid oxide fuel cells. 相似文献
4.
Vuk Uskokovi Aljoa Koak Miha Drofenik Miha Drofenik 《International Journal of Applied Ceramic Technology》2006,3(2):134-143
Silica-coated lanthanum–strontium manganite particles with La0.76 Sr0.24 MnO3+δ stoichiometric formula, exhibiting Curie temperature at ∼40°C, were prepared by using a traditional solid-state method of synthesis of magnetic ceramic particles, followed by milling and a low-temperature coating procedure in an aqueous alcoholic alkali medium. The properties of the obtained material establish it as a potential candidate for self-regulated power-absorbing and temperature-controlling materials in hyperthermia treatments. Moreover, core-comprising LaSr–manganites with different stoichiometries, ranging from La0.5 Sr0.5 MnO3+δ to LaMnO3+δ , were synthesized, with magnetic and structural properties examined thereof. Herein reported findings can potentially be used in the preparation of silica-coated magnetic particles with designable Curie temperature, offering a wide range of possibilities of adapting the material to practical instrumental setups in drug delivery and hyperthermia treatments. 相似文献
5.
A two-dimensional finite element model is developed to study the reaction kinetics and heat transfer during the self-propagating high-temperature synthesis of La0.6 Sr0.4 MnO3 , a cathode and interconnect material used in solid oxide fuel cells. The activation energy of La0.6 Sr0.4 MnO3 formation was calculated from experimental temperature history. The calculated spatial-temporal temperature profile, heat generation rate, reaction conversion, and flow pattern of surrounding gas during the reaction are reported in this work. Hot spots are found at the corner near the ignition point shortly after the ignition. The model provided a simple and reliable way to design a large-scale production of La0.6 Sr0.4 MnO3 . 相似文献
6.
Thin Yttrium-Stabilized Zirconia Electrolyte Solid Oxide Fuel Cells by Centrifugal Casting 总被引:4,自引:0,他引:4
A centrifugal casting technique was developed for depositing thin 8-mol%-yttrium-stabilized zirconia (YSZ) electrolyte layers on porous NiO-YSZ anode substrates. After the bilayers were cosintered at 1400°C, dense pinhole-free YSZ coatings with thicknesses of ∼25 μm were obtained, while the Ni-YSZ retained porosity. After La0.6 Sr0.4 Co0.2 Fe0.8 O3 (LSCF)-Ce0.9 Gd0.1 O1.95 (GDC) or La0.8 Sr0.2 MnO3 (LSM)-YSZ cathodes were deposited, single SOFCs produced near-theoretical open-circuit voltages and power densities of ∼1 W/cm2 at 800°C. Impedance spectra measured during cell tests showed that polarization resistances accounted for ∼70%–80% of the total cell resistance. 相似文献
7.
Tatsumi Ishihara Kuninobu Shimose Takanari Kudo Hiroyasu Nishiguchi Taner Akbay Yusaku Takita 《Journal of the American Ceramic Society》2000,83(8):1921-1927
A yttria-stabilized zirconia (YSZ) thin film on an La0.8 Sr0.2 MnO3 porous cathode substrate was prepared, using electrophoretic deposition (EPD) to fabricate a solid oxide fuel cell (SOFC). The electrical conductivity of an La0.8 Sr0.2 MnO3 substrate is satisfactorily high at room temperature; therefore, YSZ powder could be deposited electrophoretically onto an La0.8 Sr0.2 MnO3 substrate without any extra surface treatment, such as a metal coating. Successive repetition of EPD and sintering was required to obtain a film without gas leakage, because of the thermal expansion coefficient mismatch between the YSZ and the La0.8 Sr0.2 MnO3 substrate. On the other hand, the electromotive force of the oxygen concentration in the cell that used YSZ film prepared via EPD increased and attained the theoretical value when the number of deposition and calcination cycles was increased. Six or more successive repetitions were required to obtain a YSZ film without gas leakage. A planar-type SOFC was fabricated, using nickel as the anode and YSZ film (∼10 μm thick) that had been deposited onto the La0.8 Sr0.2 MnO3 substrate as the electrolyte and cathode. The cell exhibited an open circuit voltage of 1.0 V and a maximum power density of 1.5 W/cm2 . Thus, the EPD method could be used as a colloidal process to prepare YSZ thin-film electrolytes for SOFCs. 相似文献
8.
Hitoshi Taimatsu Keiji Wada Hiroyuki Kaneko Hiroshi Yamamura 《Journal of the American Ceramic Society》1992,75(2):401-405
The reaction of La1- x Ca x MnO3 ( x = 0, 0.1, 0.2) with ZrO2 -8 mol% Y2 O3 (YSZ) has been investigated at temperatures ranging from 1300° to 1425°C in air. Substitution of Ca for La in LaMnO3 depresses the reactivity with YSZ. A layer of La2 Zr2 O7 is formed at the La1- x Ca x MnO3 /YSZ interface after an induction period, and its formation is accelerated when the La1- x Ca x MnO3 phase is porous. The reaction proceeds by unidirectional diffusion of La, Mn, and/or Ca ions, mainly Mn ions, into YSZ. The diffusion coefficients of La and Mn ions in YSZ, which are estimated using a LaMnO3 /single-crystal YSZ couple, are much lower than that of oxygen ion. From the experimental data, a reaction mechanism is proposed. 相似文献
9.
Solid oxide fuel cells that incorporate stabilized-zirconia electrolytes commonly use the transition-metal oxide perovskite La0.875 Sr0.125 MnO3+δ as the cathode. While in operation, the cathode can be subjected to significant stresses, because of thermal expansion mismatch between mating components. The mechanical behavior of La0.875 Sr0.125 MnO3+δ has been studied using three-point bend strength measurements at ambient, 400°C, 800°C and 1000°C. The results show that phase transformations have an important role in the mechanical-strength behavior. The results also indicate some unique strengthening effects that are associated with the evolution of the unit cell with temperature and the increasing symmetry of the crystal lattice. 相似文献
10.
Novel Design of Microchanneled Tubular Solid Oxide Fuel Cells and Synthesis Using a Multipass Extrusion Process 总被引:2,自引:0,他引:2
Byong-Taek Lee A. H. M. Esfakur Rahman Jong-Hee Kim 《Journal of the American Ceramic Society》2007,90(6):1921-1925
A novel, microchanneled tubular solid oxide fuel cell was fabricated using a multipass extrusion process, with an outside diameter of 2.7 mm that contained 61 cells. Cell materials used in this work were 8 mol% yttria-stabilized zirconia (8YSZ), La0.8 Sr0.2 MnO3 (LSM), and NiO–8YSZ (50:50 vol%) as electrolyte, cathode, and anode, respectively. Three stages of heat-treatment processes were applied, at 700°C in N2 condition, at 1000°C in air, and then sintered at 1300°C for 2 h, respectively. The X-ray diffraction analysis confirmed that no reaction phases appeared after sintering. The microstructures of anode and cathode were fairly porous while the electrolyte had a dense microstructure (relative density >96%). The thickness of electrolyte, anode, and cathode were 20, 30, and 40 μm, respectively, and the diameter of the continuous channels was 150 μm. 相似文献
11.
Jong-Jin Choi Joo-Hee Lee Dong-Soo Park Byung-Dong Hahn Woon-Ha Yoon Hua-Tay Lin 《Journal of the American Ceramic Society》2007,90(6):1926-1929
Conductive La0.8 Sr0.2 MnO3 (LSM) and La0.6 Sr0.4 Co0.2 Fe0.8 O3 (LSCF) layers with a thickness of ∼10 μm were deposited on ferritic stainless steel (SS) by the aerosol deposition method, for use as an oxidation resistance-coating layer in the metallic interconnector of a solid oxide fuel cell. The coated layers were fairly dense without pores or cracks, and maintained good adhesion even after oxidation at 800°C for 100 h. The surface of the bare SS after annealing at 800°C for 100 h was covered with Cr2 O3 and Fe3 O4 oxide scales, and the electrical conductivity was sharply decreased. However, the LSM- and LSCF-coated SSs showed a surface microstructure with almost no oxidation and maintained good electrical conductivity after annealing at 800°C for 100 h. The area-specific resistance (ASR) of LSM- and LSCF-coated alloys after 100 h of oxidation at 800°C was 20.6 and 11.7 mΩ·cm2 , respectively. 相似文献
12.
Lan Zhang Yujun Zhang Y. D. Zhen San Ping Jiang 《Journal of the American Ceramic Society》2007,90(5):1406-1411
Lanthanum strontium manganite ((La0.8 Sr0.2 )0.9 MnO3 ; LSM) powder was successfully synthesized by an aqueous gel-casting technique, using carbonaceous precursors. Both thermal and X-ray diffraction analysis confirmed that the gel-casting LSM powder formed a single perovskite phase at 850°C, which is 100°–150°C lower than that of the LSM powder prepared by the conventional solid-state reaction route. The significantly reduced phase formation temperature of the gel-casting LSM powder is most likely due to the homogeneously distributed and immobilized precursor particles in a polymeric network, promoting the sintering and crystallization process. The LSM electrode prepared by the gel-cast LSM powder showed good electrocatalytic activity for the O2 reduction reaction for solid oxide fuel cells. 相似文献
13.
Tatsumi Ishihara Keiji Sato Yusaku Takita 《Journal of the American Ceramic Society》1996,79(4):913-919
An electrophoretic deposition (EPD) method was applied for the preparation of yttria-stabilized zirconia (YSZ) films for solid oxide fuel cell (SOFC) applications. Dense YSZ films with uniform thickness can be readily prepared with the EPD method by using acetylacetone or acetone as a solvent. The open-circuit voltages of SOFC, for which the YSZ films were prepared by the EPD method, increased with increasing repetitions of deposition and sintering. It was found that the open-circuit voltage exceeded 1.0 V after five repetitions. When the planar SOFC was fabricated using La0.6 Sr0.4 MnO3 as a cathode, and electroless plating Pt as an anode, the open-circuit voltage and the maximum power density attained were 1.03 V and 1.84 W·cm−2 , respectively. Consequently, it became evident that the electrophoretic deposition was a suitable processing route for the formation of gas-tight YSZ films with thickness less than 10 μm. 相似文献
14.
Sr-doped lanthanum cuprate was recently investigated as a potential cathode material for the intermediate temperature solid oxide fuel cell using yittria-stabilized zirconia as an electrolyte. The material thermal stability of cathode material against an electrolyte at an operating temperature plays an important role in the fuel cell's performance. In this study, the structural stability between Sr-doped lanthanum cuprate and 8 mol% yittria-stabilized zirconia was investigated by using the powder mixture and diffusion couple. The chemical reaction between these two materials in the temperature ranging from 800° to 1000°C was examined by X-ray diffraction analyses. The interfacial reaction behavior between electrode and electrolyte pellets of the reaction couple was examined by a grazing X-ray diffractometer, wavelength-dispersive X-ray analysis, and an electron probe microanalyzer. No reaction products were observed as these two materials co-fired at 800°C. The reaction products of pyrochlore La2 Zr2 O7 and perovskite SrZrO3 were formed when the specimens were heat treated at over 900°C. Because of the formation of these reaction products, the CuO was precipitated. Furthermore, an excess of SrZrO3 formation leads to the phase decomposition of perovskite Sr-doped lanthanum cuprate to La2− x Sr x CuO4 and CuO due to a decrease in strontium concentration in Sr-doped lanthanum cuprate. 相似文献
15.
An all-alkoxide route to films and nano-phase powders of the La0.5 Sr0.5 CoO3 perovskite is described. To our knowledge, this is the first purely alkoxide-based route to (La1− x Sr x )CoO3 , and it yields phase-pure and elementally homogeneous perovskite at 700°C by heating at 2°C/min. At 700°C, a cubic unit cell was obtained with a c =3.853Å, and after further heating to 1000°C, a rhombohedral cell could be indexed: a r =5.417 Å, αr =59.94°. Ninety to 130 nm thick films of La0.5 Sr0.5 CoO3 were obtained by spin coating. The gel-to-oxide conversion was studied in some detail, using thermo-gravimetric analysis, differential scanning calorimetry, powder X-ray diffraction, IR spectroscopy, and transmission electron microscope equipped with an energy-dispersive X-ray spectrometer. 相似文献
16.
Santanu Basu Amitava Chakraborty Parukuttyamma Sujatha Devi Himadri Sekhar Maiti 《Journal of the American Ceramic Society》2005,88(8):2110-2113
Nanocrystalline La0.9 Sr0.1 Al0.85 Co0.05 Mg0.1 O3 oxide powder was synthesized by a citrate–nitrate auto-ignition process and characterized by thermal analysis, X-ray diffraction, and impedance spectroscopy measurements. Nanocrystalline (50–100 nm) powder with perovskite structure could be produced at 900°C by this process. The powder could be sintered to a density more than 96% of the theoretical density at 1550°C. Impedance measurements on the sintered samples unequivocally established the potential of this process in developing nanostructured lanthanum aluminate-based oxides. The sintered La0.9 Sr0.1 Al0.85 Co0.05 Mg0.1 O3 sample exhibited a conductivity of 2.40 × 10−2 S/cm in air at 1000°C compared with 4.9 × 10−3 S/cm exhibited by La0.9 Sr0.1 Al0.85 Mg0.15 O3 . 相似文献
17.
Hideki Taguchi Daisuke Matsuda Mahiko Nagao Kimiaki Tanihata Yoshinari Miyamoto 《Journal of the American Ceramic Society》1992,75(1):201-202
Perovskite-type (La1- x Sr x )MnO3 (0 x 0.3) was synthesized through the sol–gel process at low temperature (400° to 500°C). Poly(acrylic acid) (PAA) was used to make a gel from an aqueous solution of lanthanum, strontium, and manganese nitrates. The particle-diameter distribution of the manganites had a maximum value of 0.3 to 0.7 μ m, and a specific surface area of about 17.5 to 23.5 m2 /g. 相似文献
18.
Tatsumi Ishiham Takanari Kudo Hideaki Matsuda Yusaku Takita 《Journal of the American Ceramic Society》1994,77(6):1682-1684
Cathodic overpotentials of Ln0.6 Sr0.4 MnO3 (Ln is La, Pr, Nd, Sm, Gd, Yb, and Y) were studied for a new cathode for solid-oxide fuel cells (SOFCs) with low overpotentials in a relatively-low-temperature region. Cathodic overpotentials strongly depended on the rare-earth cations in the A sites of the perovskite oxide. In particular, overpotentials of a Sr-doped PrMnO3 cathode maintained low values despite decreased operating temperature. Consequently, almost the same power density of a SOFC with Ln0.6 Sr0.4 MnO3 cathode was obtained at about 100 K lower operating temperature by using Sr-doped PrMnO3 as the cathode. 相似文献
19.
P. K. GALLAGHER D. W. JOHNSON JR. E. M. VOGEL 《Journal of the American Ceramic Society》1977,60(1-2):28-31
Samples of LaMn1-x Cux O3-y in the range 0≤x≤0.8 were prepared from freeze-dried solutions of the nitrates. Samples with x≤0.6 were single-phase perovskites. At higher values of x , the samples contained La2 CuO4 and CuO as well as the perovskite phase. Samples of LaMn1−x ,Cux ,O3−y supported on ceramic monoliths or when mixed with powdered A12 O3 exhibit catalytic activity for the oxidation of CO. Greatest activity is shown for 0.4≤x≤0.7. Although the catalysts are severely poisoned by SO2 , 2% H2 O in the gas stream causes only slight deactivation. Activities of other oxide catalysts were also measured and compared. Rate constants per unit surface area at 200° to 400°C follow the order Co3 O4 >Pt>LaMn1−x Cux O3−y (0.4≤x≤0.7)>copper chromite>La1−x Srx ,MnO3 ≤ other substituted LaMnO3 materials, CuO, or La2 CuO4 . The perovskite catalyst is more stable than Co3 O4 or copper chromite when heated in 10% H2 + 90% N2 . 相似文献
20.
Takehisa Fukui Takeshi Oobuchi Yumi Ikuhara Satoshi Ohara Kaseki Kodera 《Journal of the American Ceramic Society》1997,80(1):261-263
(La0.8 Sr0.2 )0.9 MnO3 –YSZ composite particles were synthesized by spray pyrolysis. The mean particle size of the synthesized powders was about 1 pm and the particle size distribution was very narrow. The synthesized powders were composed of the perovskite (La,Sr)MnO3 and cubic phase YSZ. Each particle synthesized consisted of uniform and well-dispersed line primary particles of (La,Sr)MnO3 and YSZ (0.1 μm particle size). 相似文献