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1.
Kjell Wiik Christian R. Schmidt Sonia Faaland Senem Shamsili Mari-Ann Einarsrud Tor Grande 《Journal of the American Ceramic Society》1999,82(3):721-728
Sintered submicrometer powder mixtures of strontium-substituted lanthanum manganite and yttria-stabilized zirconia have been studied in order to investigate the chemical stability of these materials as respectively electrode and electrolyte in solid oxide fuel cells. Formation of secondary phases was observed after 1 h heat treatment at 1350°C and more than 13 h at 1200°C. La2 Zr2 O7 was formed in mixtures with LaMnO3 at 1350°C, while SrZrO3 was formed in mixtures containing La0.6 Sr0.4 MnO3 or La0.4 Sr0.6 MnO3 . Only minor amounts of secondary phases were observed in mixtures with La0.7 Sr0.3 MnO3 . Chemical analysis revealed considerable interdiffusion between the primary phases as well as A-site deficiency of LaMnO3 and La0.7 Sr0.3 MnO3 when exposed to cubic zirconia. The oxidative/reductive nature of the chemical reaction between strontium-substituted lanthanum manganite and yttria-stabilized zirconia is discussed in relation to the Sr content in LSM. The lattice parameter of cubic zirconia was observed to be quite sensitive to the interdiffusion and is an excellent tool for investigating reactions on heterophase interfaces involving stabilized zirconia. 相似文献
2.
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
3.
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
4.
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
5.
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
6.
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
7.
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
8.
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
9.
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
10.
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
11.
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
12.
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
13.
Xuebin Zhu Shoubao Zhang Hechang Lei Xiangde Zhu Gang Li Bosen Wang Wenhai Song Zhaorong Yang Jianming Dai Yuping Sun Dongqi Shi Shixue Dou 《Journal of the American Ceramic Society》2009,92(4):800-804
Metallic and transparent La0.5 Sr0.5 TiO3+ x /2 films were prepared by the chemical solution deposition (CSD) method using topotactic reduction processing. The use of Si powder as the reducing agent was facile and allowed easy manipulation. It was observed that metallic (resistivity at 300 K ∼2.43 mΩ cm) and transparent (∼80% transmittance at visible light) La0.5 Sr0.5 TiO3+ x /2 films could be obtained with an annealing temperature of 900°C, which was significantly lower than the hydrogen reduction temperature (∼1400°C). The successful preparation of metallic and transparent La0.5 Sr0.5 TiO3+ x /2 films using CSD has provided a feasible route for depositing other perovskite-structured functional layers on La0.5 Sr0.5 TiO3+ x /2 films using this low-cost all CSD method. 相似文献
14.
Francesca Licci Giuseppe Turilli Patrizia Ferro Antonio Ciccarone 《Journal of the American Ceramic Society》2003,86(3):413-419
LaMn1− y 3+ Mn y 4+ O3±d and La0.67 R0.33 Mn1− y 3+ Mn y 4+ O3±d (R = Ca, Sr, Ba) phases were synthesized at 350°C by using very reactive, amorphous precursors obtained from the stoichiometric citrate solutions. The chemical process was optimized with respect to the solution concentration, pH, and additives. The precursor reactions were investigated as a function of the cation stoichiometry and the additive by simultaneous thermal and thermogravimetric analysis and X-ray diffraction. The reaction pathway was found to be independent of the cation stoichiometry, but related to the acid or base additive. The annealing temperature was systematically increased in the 350–1200°C interval and the La0.67 Sr0.33 MnO3±d properties (i.e., crystal sizes, Mn average valence, Curie temperature, magnetization, magnetic susceptibility) were measured and found to vary consistently as a function of it. 相似文献
15.
Benjamin P. McCarthy Larry R. Pederson Harlan U. Anderson Xiao-Dong Zhou Prabhakar Singh Gregory W. Coffey Edwin C. Thomsen 《Journal of the American Ceramic Society》2007,90(10):3255-3262
Exposure of (La0.90 Sr0.10 )0.98 MnO3+δ (LSM-10) to repeated oxygen partial pressure cycles (air/10 ppm O2 ) resulted in enhanced densification rates, similar to behavior shown previously due to thermal cycling. Shrinkage rates in the temperature range 700°–1000°C were orders of magnitude higher than Makipirtti–Meng model estimations based on stepwise isothermal dilatometry results at a high temperature. A maximum in enhanced shrinkage due to oxygen partial pressure cycling occurred at 900°C. Shrinkage was the greatest when LSM-10 bars that were first equilibrated in air were exposed to gas flows of lower oxygen fugacity than in the reverse direction. The former creates transient cation and oxygen vacancies well above the equilibrium concentration, resulting in enhanced mobility. These vacancies annihilate as Schottky equilibria are reestablished, whereas the latter condition does not lead to excess vacancy concentrations. 相似文献
16.
Phase equilibria of the La2 O3 –SrO–CuO system have been determined at 950°C at 30 kbar (3 GPa). Stable phases at the apexes of the ternary phase diagram are CuO, La2 O3 , and SrO. Stable intermediate phases are La2 , CuO4 and La2 Cu2 O5 in the LaO1.5 –CuO binary and Sr2 CuO3 , SrCuO2 , and Sr14 Cu24 O41 in the CuO–SrO binary. The La2– x Sr x -CuO4–δ solid solution is stable for 0.00 is ≤ x ≤ 1.29, the La2– x Sr1+ x Cu2 O6+δ solid solution is stable for 0.03 ≤ x ≤0.20, the La2– x Sr x Cu2 O5–δ solid solution is stable for 0.00 ≤ x ≤1.08, and the La x Sr14– x Cu24 O41 solid solution is stable for 0.00 ≤ x ≤ 6.15. The 30 kbar phase diagram differs from the 1 atm (0.1 MPa) and 10 kbar (1 GPa) results principally in the absence of La1– x Sr2+ x Cu2 O5.5+δ as a stable phase and the extended range of the La2– x Sr x Cu2 O5–δ solid solution at 30 kbar. 相似文献
17.
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
18.
Abhoy Kumar Parukuttyamma Sujatha Devi Abhijit Das Sharma Himadri Sekhar Maiti 《Journal of the American Ceramic Society》2005,88(4):971-973
Nanocrystalline, single phase, and highly homogeneous La0.84 Sr0.16 MnO3 (LSM) powder was prepared by a unique spray-pyrolysis process for solid oxide fuel cell applications. Atomization of a citrate–nitrate precursor solution consisting of La3+ , Sr2+ , and Mn2+ ions in the molar ratio 0.84:0.16:1.0, which can initiate a controlled exothermic anionic oxidation-reduction reaction leading to a self-propagating auto-ignition (self-ignition) reaction within individual droplets led to the conversion of the precursor to their corresponding single-phase LSM powder. Characterization of the as-sprayed and calcined products by X-ray powder diffraction, thermal analysis, and microstructural analysis confirmed the formation of nanocrystalline single-phase LSM powder by this process. 相似文献
19.
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
20.
Toshio Suzuki Piotr Jasinski Vladimir Petrovsky Harlan U. Anderson 《Journal of the American Ceramic Society》2005,88(5):1186-1189
The effects of microstructure on the optical properties of La0.4 Sr0.6 TiO3 thin films were investigated. Dense films with the thickness of ∼200 nm and grain size 14–30 nm were produced on monocrystalline sapphire substrates by using a polymeric precursor spin coating technique at annealing temperatures under 800°C. X-ray data showed the formation of a single-phase cubic perovskite-type structure similar to undoped SrTiO3 for annealing temperatures >500°C. The results of optical measurements showed that the optical spectra varied with the change of the grain size. From these data, the absorption coefficients were calculated and the band gap energy determined. In agreement with the quantum confinement model, it was shown that the band gap energy increased as the grain size decreased. 相似文献