Investigation of Yttria Stabilized Bismuth Oxide and its Application in Composite Cathodes (original) (raw)
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Sustainability
Perovskite materials have gained a lot of interest in solid oxide fuel cell (SOFC) applications owing to their exceptional properties; however, ideal perovskites exhibit proton conduction due to availability of low oxygen vacancies, which limit their application as SOFC electrolytes. In the current project, Sm was doped at the B-site of a BaCe0.7-xSmxZr0.2Y0.1O3-δ perovskite electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs). BaCe0.7-xSmxZr0.2Y0.1O3-δ electrolytes were synthesized through a cost-effective coprecipitation method and were sintered at a low sintering temperature. The effects of samarium (Sm) doping on the electrochemical performance of BaCe0.7-xSmxZr0.2Y0.1O3-δ were investigated. X-ray diffraction (XRD) analysis confirmed that the BaCe0.7-xSmxZr0.2Y0.1O3-δ electrolyte material retained the perovskite structure. The secondary phase of Sm2O3 was observed for BaCe0.4Sm0.3Zr0.2Y0.1O3-δ. Scanning electron microscopic (SEM) imaging displayed the dense...
Jurnal Kejuruteraan, 2020
A composite perovskite Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ-Sm 0.2 Ce 0.8 O 1.9 carbonate (BSCF-SDCC) coating was investigated to enhance the performance of SUS 430 stainless steel as interconnect material for solid oxide fuel cells (SOFCs). BSCF-SDCC powder was successfully obtained by low-speed wet milling method from commercial BSCF, SDC, and binary carbonates. The developed BSCF-SDCC powder were heat-treated 600 °C for 90 min, and then characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) equipped with energy-dispersive spectroscopy (EDS). FESEM revealed better morphology of BSCF-SDCC powder with heat treatment. However, XRD analysis showed the destruction of BSCF phase in the BSCF-SDCC powder after heat treatment at 600 °C. Moreover, electrophoretic deposition (EPD) of BSCF-SDCC powder in an ethanol-added dispersing agent suspension was investigated under 10 volt 10 minutes by 10 g/l. The coated samples were then heat-treated at 600 °C. The coated samples were characterized by comparing between the samples with and without heat treatment based on XRD, SEM-EDS, and area specific resistance (ASR) analyses. XRD analysis indicated BSCF phases disappeared for the samples with heat treatment. The heat-treated sample performed better coating morphology and fewer pores. The samples underwent 500 hours of air oxidation at 600°C, and ASR was measured by DC 2-point method during in situ oxidation process. The coated sample with heat treatment at 600 °C exhibited excellent low area-specific resistance reading of below 0.1 Ωcm2, which is an essential requirement for interconnect materials. After 500 h of oxidation, the XRD patterns revealed stable phase and maintained good coating morphology.
International Journal of Hydrogen Energy, 2008
Solid electrolytes are the most important and indispensable part of a solid oxide fuel cell (SOFC) where hydrogen is used as one of the fuels to obtain electricity. Bismuth vanadate used as an electrolyte in SOFC when doped with different divalent and trivalent metal ions provides good ionic conductivity. Higher temperature -phase (600.700 • C) of bismuth vanadate which exhibits a higher ionic conductivity can be stabilized at room temperature by various substitutions such as copper, aluminium and titanium and is denoted as BIMEVOX. In the present study a new series of Bi 4 V 2−x Al x O 11− (0 x 0.4) samples were prepared by taking an appropriate amount of constituent oxides. The sintered pellets were characterized by a scanning electron microscope (SEM) and an X-ray diffraction (XRD) technique. An AC conductivity measurement of all the samples in the temperature range of 200.700 • C was done. The conductivity measurement data exhibited a higher ionic conductivity for the sample doped with aluminium for the composition x = 0.2 as compared with other doped samples of the same series. Since the grain size and its phase distribution influence the conductivity to a great extent, the sintering parameter for the sample x = 0.2 was varied between 750 and 825 • C in an interval of 25 • C. The details of the conductivity behaviour of these samples along with their microstructural characteristics are presented in this paper. The Arrhenius plots clearly indicate the various slope changes, which are in agreement with the phase transitions that occur in these samples. The results are discussed in the light of vacancy formation and disorder enhancement in the doped samples. ᭧
Nanostructured Cathode Materials for Solid Oxide Fuel Cell by Oxalate Co-precipitation
A recently reported promising solid oxide fuel cell cathode material Ba x Sr 1-x Co y Fe 1y O 3 (BSCF) with y = 0.8 and x = 0.2 was fabricated in nanocrystalline form by a novel chemical alloying approach. The thermal properties, phase constituents, microstructure and elemental analysis of the samples were characterized by TGA-DSC, XRD, SEM and EDS techniques respectively. Thermodynamic modeling has been performed using a KTH-developed software (Medusa) and Spark Plasma Sintering (SPS) has been conducted to obtain the pellets of BSCF with rather high density for electrical measurements. The results show that all of the powders have cubic perovskite-type structure with high homogeneity. Finer resultant powder, compared to earlier reports, of BSCF with nanoscaled features possesses a significantly higher electrical conductivity up to 900 °C for ~92% dense pellet sintered by SPS at 1080 °C and under 50 MPa pressure. Specific conductivity values have been measured and the maximum of 63 S.cm -1 at 430 °C in air and 25 S.cm -1 at 375 °C in N 2 correspondingly show twice as much as conventional BSCF implying a high pledge for nano-BSCF as cathode material in IT-SOFC. Co-precipitation method to synthesize BSCF has vaster capability of scaling up than the conventional routes such as Sol-Gel.
Journal of Alloys and Compounds, 2019
In present work, perovskite structured proton conducting electrolyte materials BaZr 0.8 Y 0.2 (BZY), BaZr 0.8 Gd 0.2 (BZGd) and BaZr 0.8 Sm 0.2 (BZSm) synthesized by cost effective combustion method are investigated for intermediate temperature solid oxide fuel cell (IT-SOFC). The synthesized BZY, BZGd and BZSm materials are sintered at low temperature (1150 C) and the effect of low sintering temperature on electrolyte properties are also explored. Microstructure, surface morphology, elemental composition, functional group and weight loss are studied using different characterization techniques like XRD, SEM, EDX, FTIR and TGA. XRD shows cubic perovskite structure of all synthesized materials. Secondary phase of Y 2 O 3 is observed in BZY while BaO is observed in BZGd and BZSm due to low sintering temperature. SEM micrographs reveals dense microstructure of BZSm compared to BZY and BZGd. EDX analysis confirms the required material composition within all samples with no impurities. FTIR shows the presence of hydroxyl group and metal oxides and it is observed that BZY exhibit more structural symmetry compared to BZSm and BZGd. Highest conductivity observed ð2:2 Â10 À3 S=cmÞ for BZY due to its structural symmetry and characteristic to prefer B-site of perovskite. Also significant power densities of 0.34 Wcm À2 , 0.24 Wcm À2 and 0.32 Wcm À2 for BZY, BZGd and BZSm electrolytes based cells at 650 C implies that BZY, BZGd and BZSm can be used as IT-SOFC electrolytes.
This paper reports on the effect of Zirconium doping on BaCe0.85Y0.15O3-? electrolyte prepared using the citrate-EDTA complexing modified sol-gel process at calcinations temperature T=1000°C. The phase formation, Thermal analysis, Morphology, Stability and Conductivity measurements were performed on the sintered powders through Thermogravimetric analysis (TGDTA), Xray diffraction (XRD), Scanning electron microscope (SEM), EDAX, FTIR, RAMAN and LCR measurements. The crystallite size of the ceramic powders calculated from Scherrer equation is 26.49nm and microstructure of the sintered powder revealed that the average grain size is in the range of 2-3?m. Dense ceramic materials were obtained at 1300°C and the relative density is 90% of the theoretical density. The ionic conductivity of the pellet is investigated from room temperature to 500°C and is found to exhibit highest conductivity of 2.2x10-3S/cm and 2.76 x10-3S/cm at 500°C in dry air and wet air atmosphere with 3% relative humidity. Frequency dependence on the dielectric constant has been investigated at various temperatures which clarified that larger value of ?? is due to superposition of both electrolyte –electrode interfacial and space charge polarization originated from dopant-vacancies created. The conductivity increased as temperature increases with activation energy in the range 0.5eV and hence this composition is worth being an electrolyte.
Composite cathode materials Ag-Ba0.5Sr0.5Co0.8Fe0.2O3 for solid oxide fuel cells
Journal of Solid State Electrochemistry, 2014
Silver-Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) cathodes were prepared in two ways. In the first method, Ag-BSCF composite powder was prepared in ethanol solution, where Ag nanoparticles serving as a component in the preparation of Ag-BSCF composite cathodes had been previously obtained via one-step synthesis in absolute ethanol using a neutral polymer (polyvinylpyrrolidone). To the best of our knowledge, this is the first study to use a Ag sol obtained by the above method for preparation of Ag-BSCF composite powder. Then, a paste containing this powder was screen-printed on a Sm 0.2 Ce 0.8 O 1.9 electrolyte and sintered at 1,000°C. In the second technique, an aqueous solution of AgNO 3 was added to a previously sintered BSCF cathode, which was then sintered again at 800°C. The oxygen reduction reaction at the quasi-point BSCF cathode on the Sm 0.2 Ce 0.8 O 1.9 electrolyte was tested by electrochemical impedance spectroscopy at different oxygen concentrations in three electrode setup. The continuous decrease of polarization resistance was observed under polarization −0.5 V at 600°C. The comparative studies of both obtained composite Ag-BSCF materials were performed in hydrogen-oxygen IT-SOFC involving samariadoped ceria as an electrolyte and Ni-Gd 0.2 Ce 0.8 O 1.9 anode. In both cases, the addition of silver to the cathode caused an increase in current and power density compared with an IT-SOFC built with the same components but involving a monophase BSFC cathode material.
2017
This study investigated the effects of sintering temperature on the microstructure and ionic conductivity of codoped ceria electrolyte with barium and samarium as dopants. The electrolyte (Ce0.8Sm0.1Ba0.1O2-δ) powder was synthesized using the citric acid-nitrate combustion method and calcined at 900 °C for 5 h. The calcined electrolyte exhibited a cubic fluorite crystal structure with some impurity phases. The calcined powder was then pressed into cylindrical pellets using uniaxial die-pressing. The pellets were sintered at three different temperatures, i.e., 1200, 1300 and 1400 °C for 5 h. Microstructural analysis of the pellets showed that the average grain size increased with the increase in sintering temperature. The sintered densities of the pellets were measured by Archimedes’ method, and the relative density values were within the range of 78 %TD to 87 %TD as the sintering temperature increased from 1200 to 1400 °C. Electrochemical impedance spectroscopy analysis showed that ...
Sintering of oxygen ion conductive ceramics and their electrical properties
Lithuanian Journal of Physics, 2012
Oxygen ion conducting ceramics (Sc 2 O 3) 0.1 (ZrO 2) 0.9 , (Sc 2 O 3) 0.1 (CeO 2) 0.01 (ZrO 2) 0.89 and Ce 0.9 Gd 0.1 O 1.95 were sintered from powders with different specific surface areas. The produced ceramics were studied by scanning electron microscopy and impedance spectroscopy methods. Impedance spectroscopy measurements were performed in a wide frequency range of 10 Hz-3 GHz at temperatures up to 900 K in air. Temperature dependences of bulk and total ionic conductivities of ceramics were investigated. High bulk ionic conductivity of the order of 1 S/m at 900 K for 10ScSZ and 10Sc1CeSZ ceramics was achieved. Total ionic conductivity for both types of 10GDC ceramics was of the order of 0.1 S/m at 700 K.
Application of the cold sintering process to the electrolyte material BaCe0.8Zr0.1Y0.1O3-δ
Journal of The European Ceramic Society, 2020
This paper describes and discusses the application of the original sintering process named cold sintering to the electrolyte material BaCe 0.8 Zr 0.1 Y 0.1 O 3δ to enhance its densification at a temperature below that needed in a conventional sintering. This new technique enables the acceleration of the densification resulting in a more compacted microstructure with an unexpected high relative density of 83 % at only 180 ° C. A subsequent annealing at 1200 ° C further enhances the densification which reaches 94 %. The electrochemical performance of CSP sintered ceramics was investigated and optimized by varying different process parameters. The comparison with the conventional sintered material reveals an increase of the total conductivity by mostly increasing the grain boundary one. This result emphasizes the benefits of CSP to not only reduce the sintering temperature but also to enhance the electrochemical properties.