Electrical properties of samaria-doped ceria electrolytes from highly active powders

Ding, Dong; Liu, Beibei; Gong, Mingyang; Liu, Xingbo; Xia, Changrong

doi:10.1016/j.electacta.2010.03.005

Cited by 42 publications

(18 citation statements)

References 40 publications

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“…Although many other equivalent circuits have been proposed, a modified variant of Bauerle's equivalent circuit model consisting of three serial resistor‐capacitor circuits (RC circuit) is commonly used

()(, C_{1} false/ R_{1} + C_{2} false/ R_{2} + C_{3} false/ R_{3})

with resistances R i and capacitances C i . For pure and doped ceria, the bulk, grain boundary, and electrode contribution appear each as a semicircle in the Nyquist plot . For the resulting equivalent circuit, the capacitance increases from bulk to electrode contribution.…”

Section: Methodsmentioning

confidence: 99%

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The ionic conductivity of Sm‐doped ceria

Koettgen

Martin

2020

J Am Ceram Soc

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The oxygen ion conductivity of polycrystalline samples of Sm‐doped ceria and of Gd‐doped ceria is studied as a function of doping fraction and temperature using impedance spectroscopy allowing the separation of bulk and grain boundary conductivity. The introduction of a fine spacing for the Sm dopant fraction allows the clear identification of the dopant fraction leading to the largest bulk conductivity. At 267°C, the largest bulk conductivity is shown for Ce0.93Sm0.07O1.965. With increasing temperature, indications of an increase in the dopant fraction, which leads to the maximum in conductivity, are found. For the grain boundary conductivity, the maximum appears at larger dopant fractions compared to the bulk conductivity. The largest total conductivity for both dopants is again found for Sm‐doped ceria. In literature, different syntheses and sample preparation methods led to larger total conductivities for Gd‐doped ceria. In this work, we demonstrate that the variation of sintering conditions leads to scattering in the conductivity over one order of magnitude. Finally, we demonstrate that, in nominally pure cerium oxide, impurities dominate the ionic conductivity.

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()(, C_{1} false/ R_{1} + C_{2} false/ R_{2} + C_{3} false/ R_{3})

Section: Methodsmentioning

confidence: 99%

“…For pure and doped ceria, the bulk, grain boundary, and electrode contribution appear each as a semicircle in the Nyquist plot. [27][28][29][30][31] For the resulting equivalent circuit, the capacitance increases from bulk to electrode contribution.…”

Section: Methodsmentioning

confidence: 99%

The ionic conductivity of Sm‐doped ceria

Koettgen

Martin

2020

J Am Ceram Soc

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“…The Arrhenius plots of the bulk electrical conductivity of the (CeO 2 ) 0.8 (Sm 2 O 3 ) 0.2 ceramic samples ( Figure 5) show parallel straight lines resulting from fitting the conductivity data after sintering either with the application of electric field at 800 • C, 1000 • C and 1200 • C or by heating to high temperature (1500 • C), indicating that the charge carrier is the same. From the slope of the line segment, taking into account that σ = (σ 0 /T) exp − (H/kT), where σ is the conductivity at the absolute temperature T, σ 0 is the pre-exponential factor, H is the activation energy and k is the Boltzmann constant, H was evaluated as 0.74 eV and known to vary from 0.62 to 0.97 eV, depending on the powder synthesis and sintering profile, meaning that O 2− ions are the charge carriers [38].…”

Section: Discussionmentioning

confidence: 99%

Electrical Behavior of Electric Field-Assisted Pressureless Sintered Ceria-20 mol% Samaria

et al. 2019

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CeO2:20 mol% Sm2O3 green ceramic pellets were sintered conventionally at 1500 °C/2 h and flash sintered by applying a 200 V cm−1 electric field at 800 °C, 1000 °C and 1200 °C. The thickness shrinkage of the pellets was followed bythe specimen being positioned inside a dilatometer adapted with platinum electrodes and terminal leads connected to a power supply for application of the electric voltage. The microstructure of the surfaces of the sintered samples were observed in a scanning electron microscope. The electrical properties were evaluated by the impedance spectroscopy technique in the 5 Hz–13 MHz frequency range from 210 °C to 280 °C. The main results show that (i) the final shrinkage level is nearly independent of the temperature when the electric field is applied and slightly better than that of the 1500 °C sintered pellet, and (ii) the bulk conductivity of the sample flash sintered at 1200 °C is similar to that of the sample sintered at 1500 °C. The availability of a pathway for the electric current pulse derived from the applied electric field is proposed as the reason for the achieved shrinkages. Scavenging of the grain boundaries by Joule heating is proposed as the reason for the improved oxide ion bulk conductivity.

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“…The activation energy of R is independent of sintering temperature with values from 0.59 eV to 0.65 eV, which is in good agreement with literature values for the activation energy of GDC ionic conductivity. 27,28 No observable change in the activation energy of GDC indicates that Cr has no direct effect on the bulk conduction of GDC electrolyte. On the other hand, the apparent activation energy for R P after aging varies significantly with the sintering temperature, the values decreased from 1.40 to 1.10 eV with the increase of sintering temperature.…”

Section: Resultsmentioning

confidence: 99%

Long-Term Cr Poisoning Effect on LSCF-GDC Composite Cathodes Sintered at Different Temperatures

Xiong

Taillon

Pellegrinelli

et al. 2016

J. Electrochem. Soc.

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The impact of sintering temperature on Cr-poisoning of solid oxide fuel cell (SOFC) cathodes was systematically studied. La 0.6 Sr 0.4 Fe 0.8 Co 0.2 O 3-δ -Ce 0.9 Gd 0.1 O 2-δ symmetric cells were aged at 750 • C in synthetic air with the presence of Crofer 22 APU, a common high temperature interconnect, over 200 hours and electrochemical impedance spectroscopy (EIS) was used to determine the degradation process. Both the ohmic resistance (R ) and polarization resistance (R P ) of LSCF-GDC cells, extracted from EIS spectra, for different sintering temperatures increase as a function of aging time. Furthermore, the Cr-related degradation rate increases with decreased cathode sintering temperature. The polarization resistance of cathode sintered at lower temperature (950 • C) increases dramatically while aging with the presence of Cr and also significantly decreases the oxygen partial pressure dependence after aging. The degradation rate shows a positive correlation to the concentration of Cr. The results indicate that decreased sintering temperature increases the total surface area, leading to more available sites for Sr-Cr-O nucleation and thus greater Cr degradation. The growing demand for robust, inexpensive, clean, secure, and sustainable energy have stimulated great interest in fuel cells. Among all types, solid oxide fuel cells (SOFCs) are one of the most promising candidates due to high efficiency and fuel flexibility.1-4 Recently, significant effort has been devoted to the development of intermediate to low temperature (400-800• C) SOFCs. Lowing operating temperature not only decreases the degradation rates but also broadens the selections of materials. The mixed ionic and electronic conducting (MIEC) perovskite La 0.6 Sr 0.4 Fe 0.8 Co 0.2 O 3-δ (LSCF) and its composite with Ce 0.9 Gd 0.1 O 2-δ (GDC) is a promising cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs) because of its high intrinsic electrocatalytic activity to the oxygen reduction reaction (ORR) and acceptable thermal expansion coefficient. However, one of the challenges for the commercialization is the durability during long-term operation. [5][6][7][8][9] One of the most severe issues for cathode degradation is Cr-poisoning from Cr-containing stainless steel interconnects at high temperatures. Significant efforts have been given to understand the Cr-degradation mechanisms on SOFC cathodes. Jiang et al. [10][11][12] shows that gaseous Cr species can be chemically reduced and deposited at triple phase boundaries (TPB) as well as two-phase boundaries, blocking sites active toward the ORR. [10][11][12] The activity of the ORR on cathodes is governed by several factors, such as the atomic structure, surface composition 13-15 and bulk microstructure. In this research, sintering effect on Cr-degradation on LSCF-GDC was studied. Small changes in cathode sintering temperature leads to distinct differences in degradation rates for LSCF-GDC composite cathodes exposed to Cr-containing interconnect materials. Elevated cathode sinteri...

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Electrical properties of samaria-doped ceria electrolytes from highly active powders

Cited by 42 publications

References 40 publications

The ionic conductivity of Sm‐doped ceria

The ionic conductivity of Sm‐doped ceria

Electrical Behavior of Electric Field-Assisted Pressureless Sintered Ceria-20 mol% Samaria

Long-Term Cr Poisoning Effect on LSCF-GDC Composite Cathodes Sintered at Different Temperatures

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