Study of glycine nitrate precursor method for the synthesis of gadolinium doped ceria (Ce0.8Gd0.2O1.90) as an electrolyte for intermediate temperature solid oxide fuel cells (original) (raw)
Related papers
Electrolyte materials for solid oxide fuel cells derived from metal complexes: Gadolinia-doped ceria
Ceramics International, 2012
Gadolinia doped ceria (GDC) powders with different gadolinium contents were successfully prepared by the thermal decomposition of ceria complexes. All the calcined powder samples were found to be ceria-based solid-solutions having a fluorite-type structure. The powders were coldisostatically pressed and sintered in air at 1500 8C for 5 h to attain a sintered density of about 90% of its theoretical value. The electrical conductivity of the GDC pellets in air was studied as a function of temperature in the 225-700 8C range, by using two-probe electrochemical impedance spectroscopy measurements. The highest total conductivity (s 600 8C = 0.025 S/cm) was found for the Ce 0.85 Gd 0.15 O 1.925 composition.
Gd3+ and Sm3+ co-doped ceria based electrolytes for intermediate temperature solid oxide fuel cells
Electrochemistry communications, 2004
Co-doped ceria of Ce 1Àa Gd aÀy Sm y O 2À0:5a , wherein a ¼ 0:15 or 0.2, 0 6 y 6 a, were prepared for intermediate temperature solid oxide fuel cells (ITSOFCs). Their structures and ionic conductivities were characterized by X-ray diffraction and AC impedance spectroscopy. All the electrolytes were found to be ceria based solid solutions of fluorite type structures. However, co-doping effect was observed more apparent for the electrolytes with a ¼ 0:15 than for those with a ¼ 0:2. In comparison to the singly doped ceria, the co-doped ceria of Ce 0:85 Gd 0:15Ày Sm y O 1:925 , wherein 0:05 6 y 6 0:1, showed much higher ionic conductivities at 773-973 K. These co-doped ceria are more ideal electrolyte materials of ITSOFCs.
Ceramics International, 2020
The gadolinium-doped ceria is investigated as electrolyte materials for intermediate temperature solid oxide fuel cells (IT-SOFCs) due to its oxide ion conductivity. The doping of Gd 3+ to Ce 4+ can introduce a small strain in the lattice thereby improved conductivity with low activation energy is expected. The 20 mol. % gadolinium doped ceria (Ce 0.8 Gd 0.2 O 2− δ) nanocrystalline powder is prepared here by citrate-complexation method. The XRD, Rietveld refinement, FTIR, UV-Visible, FESEM/EDX, and a c-impedance techniques are used to characterize this sample. The oxide ion conductivity is determined between 523 − 1023 K. The Ce 0.8 Gd 0.2 O 2− δ shows highest oxide ion conductivity of 6.79 × 10 − 3 S cm − 1 and 1.11 × 10 − 2 S cm − 1 at 973 K and 1023 K, respectively. The Ce 0.8 Gd 0.2 O 2− δ showed lower activation energies of 1.09, 0.70, and 0.88 eV for grain, grain boundary, and total conduction, respectively. Thus, the nano crystalline Ce 0.8 Gd 0.2 O 2− δ is proposed as potential electrolyte for IT-SOFCs.
Low temperature anode-supported solid oxide fuel cells based on gadolinium doped ceria electrolytes
Journal of Power Sources, 2007
The utilization of anode-supported electrolytes is a useful strategy to increase the electrical properties of the solid oxide fuel cells, because it is possible to decrease considerably the thickness of the electrolytes. We have successfully prepared single-chamber fuel cells of gadolinium doped ceria electrolytes Ce 1−x Gd x O 2−y (CGO) supported on an anode formed by a cermet of NiO/CGO. Mixtures of precursor powders of NiO and gadolinium doped ceria with different particle sizes and compositions were analysed to obtain optimal bulk porous anodes to be used as anode-supported fuel cells. Doped ceria electrolytes were prepared by sol-gel related techniques. Then, ceria-based electrolytes were deposited by dip coating at different thicknesses (15-30 m) using an ink prepared with nanometric powders of electrolytes dispersed in a liquid polymer. Cathodes of La 1−x Sr x CoO 3 (LSCO) were also prepared by sol-gel related techniques and were deposited on the electrolyte thick films. Finally, electrical properties were determined in a single-chamber reactor where propane, as fuel, was mixed with synthetic air below the direct combustion limit. Stable density currents were obtained in these experimental conditions. Flux rate values of the carrier gas and propane partial pressure were determinants for the optimization of the electrical properties of the fuel cells.
Effect of co-dopant addition on properties of gadolinia-doped ceria electrolyte
Journal of power sources, 2000
. Various trivalent oxides were added as co-dopants to gadolinia-doped ceria GDC electrolyte used for solid oxide fuel cells at up to 5 mol%. An examination was made on how they affect the electrical conductivity of the electrolyte and, eventually, the open-circuit voltage Ž . Ž . OCV of a unit cell. Through a comparison of the thermal expansion coefficients TEC , it was investigated whether or not the co-doped electrolytes are thermomechanically compatible with other cell components. The addition of co-dopants generally improve the electrical Ž . properties of the electrolyte by yielding greater OCV values and not changing the TEC significantly 5% at most , except in the case of Ž . Pr. Among the electrolytes examined, the one co-doped with Sm 3 mol% shows the best improvement in performance. q 2000 Elsevier Science S.A. All rights reserved.
Journal of Electroceramics, 2005
In this study, we report key functional properties of gadolinium-doped ceria (Gd 0.1 Ce 0.9 O 1.95 , GDC) sintered at low temperatures as well as single-cell electrochemical performance of a single-cell prepared there of. GDC solid solutions were sintered at various temperatures ranging 1100-1400 • C and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), density measurements, mechanical strength tests and electrical conductivity measurements. The dry-pressed GDC disc sample sintered at 1100 • C was found to have 96% of the theoretical density and higher sintering temperatures led to higher densities. SEM micrographs of the fracture and plan surfaces of the sintered discs established the absence of any open pores. The sample sintered at 1100 • C exhibited high electrical conductivity of 0.027 S/cm at 650 • C. The mechanical strength of the sintered samples was determined to be in the range of 150-175 MPa. Greater than 96% of theoretical density, good mechanical strength, and high electrical conductivity of GDC disc samples sintered at 1100 • C established the viability of low-temperature processing of GDC for its use as an SOFC electrolyte. Accordingly, a single-cell was prepared by co-sintering of GDC electrolyte and LSCF-GDC cathode at 1100 • C and subsequent firing of CuO-GDC anode at 900 • C. The electrochemical performance of the cell was evaluated in H 2 fuel at 650 • C.
Investigation of the stability of ceria-gadolinia electrolytes in solid oxide fuel cell environments
Solid State Ionics, 1999
Doped ceria-based materials are potential electrolytes for use in lower operating temperature (500-700 o C) solid oxide fuel cells because of their high ionic conductivity. In this study, impedance behaviour and microstructure of the (Ce 0.8 Gd 0.2)O 1.9 exposed to mild fuel environments (H 2-N 2 mixtures) have been investigated. The exposure of specimens to H 2-N 2 mixtures at 1000 o C resulted in a substantial expansion of the lattice as a consequence of the reduction of Ce 4+ to Ce 3+ , which in turn led to the development of microcracks and loss of continuity at the grain boundary region and increase in both the grain boundary (major effect) and the lattice (minor effect) resistivity. The behaviour for the grain boundary resistivity after the 800 o C exposure was somewhat similar although expansion of the lattice at 800 o C (or lower temperatures) was considerably less conspicuous. After exposure to H 2-N 2 atmosphere at lower temperatures (650 and 500 o C), although no significant increase in the grain boundary resistivity for exposures up to 1000 hours was observed, the shape of the grain boundary arc was clearly affected. The large increase in the grain boundary resistivity in reduced specimens has been attributed to the observed microcracking, loss of continuity between grains and possibly the formation of new phase regions with extremely poor oxygen-ion conductivity along grain boundaries during the reduction. The disruption to the microstructure is not recovered on subsequent oxidation in air.
Microwave-assisted synthesis of gadolinia-doped ceria powders for solid oxide fuel cells
Ceramics International, 2011
Gadolinia doped ceria (GDC) is an attractive electrolyte material for intermediate temperature solid oxide fuel cells (IT-SOFCs) for its high ionic conductivity at low temperature (500-700 8C). A number of different methods are currently used to prepare nano-sized doped-ceria powder. Among the others, precipitation in solution remains the best method to obtain well-dispersed particles of controlled properties. In this work, nanocrystalline Ce 1Àx Gd x O 2Àd (GDC) particles were produced by polyol microwave assisted method in very mild conditions (170 8C, 2 h, 1 atm). The as-synthesized powder showed good sinterability and ionic conductivity comparable to the ones of the corresponding nanometric commercial GDC. #
Study on Gd 3+ and Sm 3+ co-doped ceria-based electrolytes
Journal of Solid State Electrochemistry, 2005
Doped ceria electrolytes of Ce 1-a Gd a-y Sm y O 2-0.5a , wherein a=0.15 or 0.2, and 0 £ y £ a, were prepared with the citrate method, and characterized by inductively coupled plasma-atomic emission spectrometry, energy dispersive spectrometry, scanning electron microscopy, powder X-ray diffraction, and AC impedance spectroscopy. The effect of composition on the structure and conductivity was studied. All the samples were fluorite-type ceria-based solid solutions. For the singly doped samples, the optimal composition was Ce 0.85 Gd 0.15 O 1.925 for Gd 3+ -doped ceria (CGO), which showed higher ionic conductivity than the best Sm 3+doped ceria (CSO) at 773-973 K. For the co-doped samples, the ionic conductivities were higher than those of the singly doped ones in the temperature range 673-973 K when a=0.15, but only better in 673-773 K when a=0.2. For the samples of Ce 0.85 Gd 0.15-y Sm y O 1.925 , wherein 0.05 £ y £ 0.1, much higher ionic conductivity was observed than those of the singly doped ceria at 773K$973 K. Therefore, these co-doped samples would be better than CGO and CSO to be the electrolytes of intermediate-temperature solid oxide fuel cells.
Ultra-fine Gd-doped ceria (GDC) powders were synthesized via co-precipitation using ammonium car-bonate as the precipitant. The crystallite size of the resultant GDC powders was measured as ~33 nm. The dilatometry test of the powder compacts and the relative density measurement of sintered pellets with various sintering temperatures revealed the synthesized nano-GDC powders had superior sinterability compared to commercial GDC powders (e.g., 96% vs 78% in relative density at 1300 C, respectively). Based on the total conductivity measurement of the co-precipitated GDC via electrochemical impedance spectroscopy, we found there was an optimum sintering temperature range (1300e1400 C) to achieve both high density and high conductivity due to significant increase in grain boundary resistance at higher temperature (1500 C). Moreover, the nano-sized and highly sinterable co-precipitated GDC effectively enhanced oxygen reduction reaction at the La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3Àd /GDC composite cathode due to increase in active reaction sites as well as enhanced phase connectivity in 3D-bulk at lower sintering temperatures.