共查询到20条相似文献,搜索用时 31 毫秒
1.
Xiaoliang Zhou 《Materials Research Bulletin》2007,42(8):1582-1588
In this paper, an interconnecting ceramic for solid oxide fuel cells was developed, based on the modification from La0.7Ca0.3CrO3−δ by addition of Ce0.8Sm0.2O1.9. It is found that addition of small amount Ce0.8Sm0.2O1.9 into La0.7Ca0.3CrO3−δ dramatically increased the electrical conductivity. For the best system, La0.7Ca0.3CrO3−δ + 5 wt.% Ce0.8Sm0.2O1.9, the electrical conductivity reached 687.8 S cm−1 at 800 °C in air. In H2 at 800 °C, the specimen with 3 wt.% Ce0.8Sm0.2O1.9 had the maximal electrical conductivity of 7.1 S cm−1. With the increase of Ce0.8Sm0.2O1.9 content the relative density increased, reaching 98.7% when the Ce0.8Sm0.2O1.9 content was 10 wt.%. The average coefficient of thermal expansion at 30-1000 °C in air increased with Ce0.8Sm0.2O1.9 content, ranging from 11.12 × 10−6 to 12.46 × 10−6 K−1. The oxygen permeation measurement illustrated a negligible oxygen ionic conduction, indicating it is still an electronically conducting ceramic. Therefore, this material system will be a very promising interconnect for solid oxide fuel cells. 相似文献
2.
The densification behavior and grain growth of Ce0.8Gd0.2O1.9 ceramics were investigated with the gallia concentration ranging from 0 to 10 mol%. Both the sintered density and grain size were found to increase rapidly up to 0.5 mol% Ga2O3, and then to decrease with further additions. Under the same sintering conditions, the samples with 3 mol% Ga2O3 and less exhibited a higher sintered density, as compared to the one without Ga2O3 addition. However, a pinning effect on grain growth was found at 2 mol% Ga2O3. In the dopant content range of 0 to 10 mol%, 0.5 mol% Ga2O3 was the optimum doping level in promoting densification and grain growth of commercially available powders of Ce0.8Gd0.2O1.9. 相似文献
3.
J.-G. Kim W.-P. Tai J.-M. Lee J.-G. Ha S.-M. Lim 《Journal of Materials Science: Materials in Electronics》2004,15(4):241-245
We fabricated porous (Ba,Sr)(Ti,Sb)O3 ceramics by adding potato-starch (1–20 wt %) and investigated the effects of sintering temperature (1300–1450 °C) and time (0.5–10 h) on the positive temperature coefficient of resistivity characteristics of the porous ceramics. The room-temperature electrical resistivity of the (Ba,Sr)(Ti,Sb)O3 ceramics decreased with increasing sintering temperature, while that of the ceramics increased with increasing sintering time. For example, the room-temperature electrical resistivity of the (Ba,Sr)(Ti,Sb)O3 ceramics for the samples sintered at 1300 °C and 1450 °C for 1 h is 6.8×103 and 5.7×102 cm, respectively, while that of the ceramics is 6.5×102 and 1.3×107 cm, respectively, for the samples sintered at 1350 °C for 0.5 h and 10 h. In order to investigate the reason for the decrease and increase of room-temperature electrical resistivity of the samples with increasing sintering temperature and time, the average grain size, porosity, donor concentration of grains (N
d), and electrical barrier height of grain boundaries () of the samples are discussed. 相似文献
4.
La1.6Sr0.4NiO4+δ-Ce0.8Sm0.2O1.9 composite cathodes were prepared successfully using combustion synthesis method for intermediate temperature solid oxide fuel cells. The chemical compatibility, thermal expansion behavior, electrical conductivity and electrode performance were studied. The X-ray diffraction of La1.6Sr0.4NiO4+δ-Ce0.8Sm0.2O1.9 composite result proved a slight reaction between La1.6Sr0.4NiO4+δ and Ce0.8Sm0.2O1.9. Both the thermal expansion coefficient and the electrical conductivity of La1.6Sr0.4NiO4+δ-Ce0.8Sm0.2O1.9 decreased with increasing Ce0.8Sm0.2O1.9 content. AC impedance spectroscopy measurements indicated that the addition of 30 wt% Ce0.8Sm0.2O1.9 to La1.6Sr0.4NiO4+δ exhibited the lowest polarization resistance (0.238 Ωcm2) at 800 °C in air, which was only one fourth of the La1.6Sr0.4NiO4+δ electrode measured at the same temperature. 相似文献
5.
Three different SnO2-based powder mixtures, containing 2 wt% CuO as sintering aid and Sb2O3 in amounts from 0 to 4 wt% as activator of the electrical conductivity, were sintered to high density at temperatures in the range 1000–1400°C and soaking times from 1 to 6 h. Densification behaviour and microstructure development are strongly dependent on the presence of CuO, that gives rise to a liquid phase, and on Sb2O3 that retards the liquid phase formation and hinders grain growth. Cu and Sb cations can enter s.s. in the SnO2 network with different oxidation states and in different positions, depending on the sintering conditions. The characteristics of the grain boundary phase, of the SnO2 solid solutions and their modification depending on thermal treatments were analyzed. The electrical resistivity values varied in a wide range from 10–1 to 104 cm, depending on starting composition and processing conditions: in terms of the final density and of the electrical conductivity, the optimal sintering conditions were found to be 1200°C, for 1–3 h. The electrical resistivity was related to the microstructural features, particularly to the characteristics of the resulting SnO2-based solid solutions. 相似文献
6.
Microstructures and properties of sintered CdS films on glass substrates and sintered CdTe films on polycrystal CdS substrates have been investigated. The CdS films, which contained 9 wt % CdCl2 as a sintering aid and were sintered at 650° C for 1 h in nitrogen, are transparent and have an average grain size of 15m and an electrical resistivity of 0.5cm. The CdTe films, which were coated on the sintered CdS substrate and were sintered above 610° C for 1 h in nitrogen, have a dense structure with an average grain size larger than 5m. All polycrystal CdS/CdTe solar cells were fabricated by this successive coating and sintering method. The sintering temperature of CdTe films on the sintered CdS films was varied from 585 to 700° C. Compositional interfaces and p-n juctions are formed during sintering. The highest solar efficiency (7.18%) was found in a solar cell made by sintering the composite layer of glass-CdS-CdTe at 625° C for 1 h. A fabrication temperature below 610° C resulted in poor solar cell efficiencies due to the porous structure of the CdTe films and above 650° C also resulted in poor efficiencies due to the formation of a CdS1-x
Tex layer at the interface and a large p-n junction depth. 相似文献
7.
Composites of SiC-TiC containing up to 45 wt% of dispersed TiC particles were pressureless sintered to 97% of theoretical density at temperatures between 1850°C and 1950°C with Al2O3 and Y2O3 additions. An in situ-toughened microstructure, consisted of uniformly distributed elongated -SiC grains, matrixlike TiC grains, and yttrium aluminum garnet (YAG) as a grain boundary phase, was developed via pressureless sintering route in the composites sintered at 1900°C. The fracture toughness of SiC-30 wt% TiC composites sintered at 1900°C for 2 h was as high as 7.8 MPa·m1/2, owing to the bridging and crack deflection by the elongated -SiC grains. 相似文献
8.
Wei Zhou Zong Ping Shao Ran Ran Wan Qin Jin Nan Ping Xu 《Materials Research Bulletin》2008,43(8-9):2248-2259
Nano-crystalline Sm0.2Ce0.8O1.9 (SDC), Gd0.2Ce0.8O1.9 (GDC), La0.6Sr0.4Co0.2Fe0.8O3?δ (LSCF) and NiO (65 wt.%)–GDC powders for applications in solid-oxide fuel cells were synthesized by employing cotton fibers as the micro-bioreactor. As compared with the conventional glycine-nitrate (GN) combustion method, this novel process allows the preparation process to be more environmental-friendly. Furthermore, the particle size of obtained powders could be smaller, attributing to the blocking effect of cellulose on suppressing the particle contact during synthesis. By this innovative method, SDC powder with a particle size as small as ~10 nm, was obtained, which can be easily sintered to dense electrolytes at 1350 °C. The process is also capable for large-scale synthesis. 相似文献
9.
Xibao Li Gangqin Shao Xiaohua Yu Jian Wang Hongxing Gu 《Journal of Materials Science: Materials in Electronics》2011,22(2):189-192
Ce0.8Sm0.2O1.9 (SDC) powder was synthesized by spray pyrolysis at 650 °C. XRD results showed that phase-pure SDC powder with an average
crystallite size of 11 nm was synthesized. SDC electrolyte film was prepared by tape casting and sintered at different temperatures
of 1,300, 1,400 and 1,500 °C for 2 h, respectively. The SDC electrolyte film was relatively denser and showed finer microstructure
at relatively lower temperature of 1,400 °C, which might be due to the high sintering activity of the spray pyrolysis SDC
powder. The ionic conductivity of the SDC electrolyte film sintered at 1,400 °C reached a maximum value of 9.5 × 10−3 S cm−1 (tested at 600 °C) with an activation energy for conduction of 0.90 eV. 相似文献
10.
High density sub-microcrystalline Ce0.8Gd0.2O1.9 (CGO) ceramics using an unconventional two-step sintering (TSS) process have been successfully obtained. Impedance spectroscopy has been used to measure conductivity of CGO samples between 283 and 422 °C. The CGO ceramic samples sintered using the TSS process have been found to deliver superior physical and electrical properties compared to those processed employing the single-step sintering process. 相似文献
11.
Undoped and Nb-doped SrTiO3 specimens with excess titania compositions were prepared by sintering in air at 1420 or 1480 °C. Large grains due to liquid-phase sintering were obtained for undoped specimens containing 0.6 mol % excess titania and fired at 1480 °C. On the other hand uniform fine grains were observed for samples fired at 1420 °C, resulting from grain-growth inhibition due to exsolved TiO2 second phase. The solubility of excess titania seemed less than 0.2 mol% under our experimental conditions. The microstructural behaviour of Nb-doped SrTiO3 could be explained well by the Sr-vacancy compensation model. According to this model, the solubility of excess titania in SrTiO3 increased with Nb2O5 dopant concentration. Thus, for specimens which had high excess titania compositions and were sintered at 1480 °C, large grains were observed when the Nb content was low enough to retain sufficient excess titania-forming liquid phase. For specimens having the same compositions and fired at 1420 °C, uniform fine grains were obtained due to grain growth inhibition by the exsolved TiO2 second phase, when the Nb content was low. If the excess titania was less than the solubility determined by the amount of Nb dopant, Ruddlesden-Popper-type phases were believed to be formed and resulted in poor densification. Although excess titania was the major factor in determining the grain size of the specimens, the niobium dopant enhanced grain growth. 相似文献
12.
Perovskite type oxides Ln0.6Sr0.4Co0.8Mn0.2O3−δ (Ln=La, Gd, Sm, or Nd) have been prepared by the solid state reaction of corresponding oxides. The crystal parameters of the compositions were determined by XRD powder diffraction, which revealed that all the compositions have orthorhombic structure. The reaction test of all samples with Ce0.8Gd0.2O1.9 was carried out at 1200 °C for 48 h, and no reaction product was detected by XRD. The change in mass of La0.6Sr0.4Co0.8Mn0.2O3−δ as a function of temperature was determined by thermogravimetric analysis (TGA). The electrical conductivity of the sintered samples were measured as a function of temperature from 200 to 1000 °C. The highest conductivity of about 1400 S cm−1 was found in La0.6Sr0.4Co0.8Mn0.2O3−δ. The cathodic polarization of these oxides electrodes deposited on Ce0.8Gd0.2O1.9 tablet was studied at 500-800 °C in air. 相似文献
13.
Alumina powders (average grain size: 50 m) coated with TiN film of thickness 0.5 and 1.2 m were prepared by rotary powder-bed chemical vapour deposition for 15 and 90 min, respectively. These Al2O3-TiN composite powders were hot-pressed at 1800 °C and 40 MPa for 30 min. The microstructure of the Al2O3-TiN sintered composite was composed of a TiN network homogeneously distributed on the grain boundaries of alumina. The mechanical properties (hardness, bending strength and fractured toughness) and thermal conductivity of the sintered composite were found to depend on the composition and microstructure of the sintered composite, even with a small content (3–7 wt%) of TiN. The resistivity of the sintered composite was 10–1-10–3 cm. The relatively high electrical conductivity of the Al2O3-TiN composite was caused by the grain boundary conduction of TiN. 相似文献
14.
A highly stable perovskite cathode material, Ba0.5Sr0.5(Co0.6Zr0.2)Fe0.2O3−δ (BSCZF) for intermediate temperature solid-oxide fuel cells (IT-SOFCs) was synthesized via the improved EDTA-citric acid complexing technique combined with high-temperature sintering. The product was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical impedance spectra (EIS) measurements. An electrolyte-supported BSCZF/SDC/Ni-SDC fuel cell was fabricated to evaluate the performance of the material. The XRD study indicates that the sintering temperature higher than 950 °C is sufficient to the formation of clean single BSCZF perovskite phase. Due to the incorporation of Zr ions, BSCZF perovskite exhibit lower electrical conductivity with higher activation energy but higher structural stability than the Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) parent oxide. The maximum electrical conductivity of BSCZF attains 16.9 S cm−1 at around 540 °C. Impedance spectra showed that the ASRs of BSCZF cathode on samaria doped ceria (Ce0.8Sm0.2O1.9, SDC) electrolyte are low but are still slightly larger than those of BSCF at similar conditions. The BSCZF/SDC/Ni-SDC cell exhibited a stable output with the maximum power densities of 30, 75, 139 and 241 mW cm−2 at 550, 600, 650 and 700 °C, respectively. Due to the high electrochemical performances as well as the excellent stability, BSCZF perovskite may be an attractive cathode material for IT-SOFCs. 相似文献
15.
La0.6Sr0.4Co0.2Fe0.8O3?δ–Ce0.8Sm0.2O2?θ–CuO composite cathodes were studied for the potential application in intermediate temperature solid oxide fuel cells. Ce0.8Sm0.2O2?θ electrolyte with porous Ce0.8Sm0.2O2?θ interlayer was successfully prepared by one-step sintering process. The effect of interlayer between cathode and electrolyte and CuO on the electrochemical performance of the composite cathodes was investigated by AC impedance spectroscopy. The application of interlayer decreased the area specific resistance of La0.6Sr0.4Co0.2Fe0.8O3?δ–Ce0.8Sm0.2O2?θ cathode. The addition of CuO to La0.6Sr0.4Co0.2Fe0.8O3?δ reduced the phase formation temperature of La0.6Sr0.4Co0.2Fe0.8O3?δ by 150 °C and the addition of CuO to La0.6Sr0.4Co0.2Fe0.8O3?δ–Ce0.8Sm0.2O2?θ cathode reduced the optimal calcination temperature of the cathode to 800 °C. The composite cathode with 2 mol% CuO calcined at 800 °C exhibited the lowest area specific resistance of 0.05 Ω cm2 at 700 °C in air, which was reduced by 67% compared with that of La0.6Sr0.4Co0.2Fe0.8O3?δ–Ce0.8Sm0.2O2?θ cathode. The studies of the corresponding single cell performance, thermal expansion and thermal cycling behaviors further indicated that the composite cathode with 2 mol% CuO could be a promising cathode material. 相似文献
16.
We have studied nonaqueous suspensions of Ce0.8Sm0.2O1.9 (CSO), Ce0.8Gd0.2O1.9 (CGO), and Се0.8(Sm0.75Sr0.2Ba0.05)0.2O2–δ (CSSBO) nanopowders produced by laser evaporation of a target. The nanoparticles were nearly spherical in shape and their average diameter was 9, 7, and 15 nm, respectively. Using ultrasonic processing, we obtained stable nanopowder suspensions in an isopropanol + acetylacetone mixed medium, investigated their particle size composition, evaluated their zeta potential as a function of pH, and obtained potentiometric titration curves. The starting nanopowder suspensions have been shown to be weakly acidic and have a rather high initial zeta potential. During titration of the nanopowder suspensions with 0.17 N KOH in isopropanol, no isoelectric point was observed. The maximum positive values of the zeta potential, favorable for electrophoretic deposition (EPD), were reached in weakly acidic media in the pH range 4–6. Using EPD, we obtained a coating from a stable self-stabilized CSSBO suspension (ζ = +31 mV, pH 4.0), which was then sintered in air at a temperature of 1400°C. Our results demonstrate that the starting nonaqueous suspensions of the CSO, CGO, and CSSBO nanopowders suit well for producing gas-tight, homogeneous solid oxide fuel cell coatings by EPD. 相似文献
17.
Z. Khakpour A. Maghsoudipour A. A. Youzbashi K. Ahmadi 《Journal of Materials Science: Materials in Electronics》2012,23(3):786-794
The densification behavior of nanocrystalline Gd-doped ceria electrolyte, synthesized via mechanical alloying process, was
investigated by means of the conventional pressure less sintering and the two-step sintering methods. The effect of the heating
rate and the amounts of dopant on the sinterability of Ce1−x
Gd
x
O(2−δ)
x = 0.2 (2GDC) and x = 0.3 (3GDC) oxides was studied, which indicated that the gadolinium retards densification and grain growth in the final
state of the conventional sintering and 2GDC samples reach 94% density at 1,550 °C. Subsequent investigation on the grain
growth in the fully densified ceramics showed that lowering of the heating rate and increasing of the soaking time reduce
the effect of dopant and cause samples to be densified to the higher theoretical density (97%) at lower temperatures (1,400 °C).
Fully dense Gd-doped ceria ceramics with finest grain size (900–1,100 nm) can be obtained by two-step sintering method. Electrical
conductivity measurement in the GDC samples was studied by impedance spectroscopy. The grain boundary conductivity in these
specimens obtained by two-step sintering method was compared with normal sintered specimens. It is concluded that the reduced
conductivity observed in the two-step sintering specimen is attributable to the microstructure changes obtained by increased
of grain boundary resistivity. 相似文献
18.
Based on the conventional interconnect La0.7Ca0.3CrO3−δ, a novel ceramic interconnect for intermediate temperature solid oxide fuel cells was developed. In the air, the electrical conductivities of La0.7Ca0.3CrO3−δ + 5%Ce0.8Sm0.2O1.9 at 600, 700 and 800 °C were 96.7, 146.3 and 687.8 S cm−1, respectively, which increased significantly as compared with La0.7Ca0.3CrO3−δ under the same conditions. Similarly, in pure hydrogen, La0.7Ca0.3CrO3−δ + 3%Ce0.8Sm0.2O1.9 possessed the maximal electrical conductivities which were 4.2, 5.3 and 7.1 S cm−1, respectively at 600, 700 and 800 °C. The crystal structures of La0.7Ca0.3CrO3−δ, La0.7Ca0.3CrO3−δ + 5%Ce0.8Sm0.2O1.9 and La0.7Ca0.3CrO3−δ + 10%Ce0.8Sm0.2O1.9 were single phase with hexagonal symmetry, cubic phase plus some doped ceria impurity and orthorhombic phase plus some doped ceria impurity, respectively. The difference between the crystal structures may account for the difference between the electrical conductivities. The electrical conductivities and sinterability of La0.7Ca0.3CrO3−δ were increased by introducing Ce0.8Sm0.2O1.9, whereas the other properties were not influenced. 相似文献
19.
Zhimin Li Toshiyuki Mori Pengfei Yan Yuanyuan Wu ZhiPeng Li 《Materials Science and Engineering: B》2012,177(17):1538-1541
In this work, the effect of two frequently used GdxCe1−xO2−x/2 electrolytes (x = 0.1 and x = 0.2) on the performance of fuel cells operated at intermediate temperature was studied. The microstructures of ceria electrolytes responsible for the performance were discussed. Electrochemical measurements of as-prepared cells showed that the cell with Gd0.2Ce0.8O1.9 electrolyte had a better performance than that of Gd0.1Ce0.9O1.95. It can be concluded that the increase of grain boundary conductivity of Gd0.2Ce0.8O1.9 electrolyte contributes to its better cell performance. 相似文献
20.
H. M. Al-Allak T. V. Parry G. J. Russell J. Woods 《Journal of Materials Science》1988,23(3):1083-1089
The effect of AI additions on the electrical behaviour of positive temperature coefficient of resistance (PTCR) BaTiO3 ceramic sintered in air at temperatures ranging between 1220 and 1400° C have been investigated. Two batches of material, both showing a PTCR effect, were prepared identically except that additions of AI2O3 (0.55 mol %) were made to one of them. It has been confirmed that the presence of aluminium results in an increase in the temperature at which the maximum resistivity, max, occurs as well as reducing the sintering temperature, in the presence of silicon, to 1240° C. Additionally, direct comparisons between the two materials have demonstrated that such additions result in an increase of 100% in the minimum resistivity, min, at sintering temperatures beyond 1280° C. A similar increase in max for sintering temperatures below 1360° C and a five-fold reduction in the ratio of max/min in samples sintered above 1320° C have also been attributed to the presence of aluminium. It was further found that aluminium increases the average grain size by 30% and promotes the formation of a liquid phase. 相似文献