Grain size effect on the electrical properties of nanocrystalline ceria

Lee, Kyung-Ryul; Lee, Jong-Ho; Yoo, Han‐Ill

doi:10.1016/j.jeurceramsoc.2014.02.035

Cited by 29 publications

(11 citation statements)

References 27 publications

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“…The reduction in impedance of grain boundaries could be resorted to the development of CAO grains and the reduction in grain‐boundary barriers. As mentioned above, the addition of the aluminosilicate glass brings in the grain growth, which will reduce the density of grain boundary, thus reduce the conduction of grain boundaries on the impedance . Besides, the suitable addition of glass will reduce the existence of impurity phase in the grain boundaries and the defect density in grains, and thus lowers the Schottky barriers of the grain boundaries, and improve the transportation of carriers between grains.…”

Section: Resultsmentioning

confidence: 99%

Improvement in electrical properties of thermoelectric CuAlO₂ ceramics aided by aluminosilicate glass

Zhu

Zheng

et al. 2018

Int J Applied Ceramic Tech

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Delafossite CuAlO2 (CAO) ceramics were fabricated by the solid‐state route, using aluminosilicate glass powders as a sintering aid to improve the sintering ability and electrical conductivity, at 1473 K for 3 hours. The CAO ceramics with glass addition obviously enhanced bulk density, grain size, and electrical conductivity. It is found that the conductivity of CAO ceramics increased with the increase in glass content under 9.5%, whereas it was over 9.5%, the conductivity went down. The glass coming up to 9.5% increased the sintering ability and the electrical conductivity which was increased by one order of magnitude, thus increasing the figure of merit ZT for thermoelectric performance of our CAO added with 9.5% glass up to 9.82 × 10−3 at 773 K, which is a high value among the CAO ceramics. Besides, the impedance analysis shows that the impedance of the CAO ceramic was controlled by its grain boundary.

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Section: Resultsmentioning

confidence: 99%

Improvement in electrical properties of thermoelectric CuAlO₂ ceramics aided by aluminosilicate glass

Zhu

Zheng

et al. 2018

Int J Applied Ceramic Tech

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“…17,26,27 The small tale observed in the low frequency regime is known to result from electrode contribution which is dependent on the DC bias. 23,49 The Nyquist plots of as-deposited film at different temperatures are shown in Fig. S5 as a representative.…”

Section: Resultsmentioning

confidence: 99%

Thermally-Induced Dopant Segregation Effects on the Space Charge Layer and Ionic Conductivity of Nanocrystalline Gadolinia-Doped Ceria

Bae

Lim

Park

et al. 2016

J. Electrochem. Soc.

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Grain boundaries are known to block ionic conduction across grain boundaries in oxide ion conductors due to adjacent space charge layers. Since the positively charged grain boundary core is intensified with a high local concentration of defects such as oxygen vacancies, uniform distribution of a dopant may mitigate the formation of space charge layers and enhance the ionic conductivity. To investigate the dopant segregation effect on the space charge layer and ionic conductivity, we provided thermal energy to nanocrystalline gadolinia-doped ceria (GDC) thin film by post-annealing at different temperatures of 700 • C, 900 • C, and 1100 • C. STEM-EELS analysis demonstrates strong dopant segregation and a higher Ce 3+ content near the grain boundary than in the bulk after post-annealing. The concurrent segregation of dopants and Ce 3+ ions implies that once thermal treatment is applied to nanocrystalline GDC thin films, complete space charge layers are formed while the non-thermally treated GDC film with a uniform distribution of dopants has less of a space charge effect and exhibits superior ionic conductivity.Nanocrystalline materials have attracted a great deal of attention for applications in various energy conversion and storage systems including rechargeable lithium ion batteries, oxygen/ozone gas sensors, oxygen storage systems, and solid oxide fuel cells (SOFCs). 1-5 Compared to macro-or micro-scale materials, nanocrystalline materials possess extraordinary electrical or electrochemical properties (i.e., ionic conduction or surface exchange reactions). One major cause of the unusual properties is related to the fine grain size (<100 nm), which corresponds to an extremely high grain boundary density. For instance, nanocrystalline calcium oxide-stabilized zirconia (0.14 um grain size) showed a 15 times higher specific grain boundary conductivity than microcrystalline materials (>4 um grain size). 6 In terms of the surface kinetics, a nanocrystalline interlayer (∼65 nm grain size) applied to the interface between the cathode and electrolyte of a SOFC exhibited a 5-6 times lower electrode interface resistance than a microcrystalline interlayer (∼6 um grain size). 7 Therefore, understanding the grain boundary properties is important to appropriately utilize nanocrystalline materials for energy conversion devices due to their exceptional features compared to bulk materials.Recently, oxide ion conductors (e.g., gadolinia-, samaria-, or yttriadoped ceria (GDC, SDC, or YDC)) usually with a polycrystalline structure, have been widely studied as electrolyte materials for lowtemperature SOFCs (LT-SOFCs) since they exhibit higher ionic conductivity and surface exchange rate than the most commonly used electrolyte, yttria-stabilized zirconia (YSZ), especially in the low operating temperature regime (<500 • C). 7-9 In terms of the ionic conductivity, polycrystalline acceptor-doped ceria has shown grain boundary blocking of ionic conduction originating from the space charge effect. 10-14 A high local concentration of oxygen...

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“…One oxide system whose grain boundaries have received much attention is the fluorite‐structured oxide CeO 2 . The total ionic conductivity of the solid solutions CeO 2 ‐ M 2 O 3 is sufficiently high that the materials find application as oxygen‐ion conducting electrolytes in intermediate temperature solid oxide fuel cells, despite pristine grain boundaries exhibiting substantially lower conductivity than the bulk phase.…”

Section: Introductionmentioning

confidence: 99%

Analyzing the grain‐boundary resistance of oxide‐ion conducting electrolytes: Poisson‐Cahn vs Poisson‐Boltzmann theories

2019

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The diminished conductivity of pristine grain boundaries in oxide‐ion conducting electrolytes, such as (Ce,Gd)O2 and (Zr,Y)O2, is widely interpreted with the Mott‐Schottky space‐charge model, or less frequently, with the Gouy‐Chapman space‐charge model. Although routinely applied to the entire compositional range of solid solutions, from dilute to concentrated, these models, being based on the Poisson‐Boltzmann formalism, are limited in their range of validity to dilute solutions of point defects. Analyzing the grain‐boundary properties of concentrated solid solutions with such models is expected to lead to errors and inconsistencies. In this study, we employ Poisson‐Cahn theory to analyze literature data for the grain‐boundary resistance of CeO2‐Gd2O3 materials as a function of Gd concentration. Poisson‐Cahn theory combines the Cahn‐Hilliard theory of inhomogeneous systems with the Poisson equation of electrostatics and it is valid over the entire compositional range. We treat the realistic case of a restricted equilibrium: Gd accumulation profiles are frozen‐in from sintering temperatures, while the oxygen‐vacancy distributions are in equilibrium at sintering and (much lower) measurement temperatures. Data for the grain‐boundary resistance are also analyzed with the standard analytical expressions from the Mott‐Schottky and Gouy‐Chapman models. Outside the domain of their validity, these expressions are found to perform poorly. In general, we emphasize the importance of treating the interfacial properties of concentrated solid solutions with physically appropriate theories.

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Grain size effect on the electrical properties of nanocrystalline ceria

Cited by 29 publications

References 27 publications

Improvement in electrical properties of thermoelectric CuAlO₂ ceramics aided by aluminosilicate glass

Improvement in electrical properties of thermoelectric CuAlO₂ ceramics aided by aluminosilicate glass

Thermally-Induced Dopant Segregation Effects on the Space Charge Layer and Ionic Conductivity of Nanocrystalline Gadolinia-Doped Ceria

Analyzing the grain‐boundary resistance of oxide‐ion conducting electrolytes: Poisson‐Cahn vs Poisson‐Boltzmann theories

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Grain size effect on the electrical properties of nanocrystalline ceria

Cited by 29 publications

References 27 publications

Improvement in electrical properties of thermoelectric CuAlO2 ceramics aided by aluminosilicate glass

Improvement in electrical properties of thermoelectric CuAlO2 ceramics aided by aluminosilicate glass

Thermally-Induced Dopant Segregation Effects on the Space Charge Layer and Ionic Conductivity of Nanocrystalline Gadolinia-Doped Ceria

Analyzing the grain‐boundary resistance of oxide‐ion conducting electrolytes: Poisson‐Cahn vs Poisson‐Boltzmann theories

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Improvement in electrical properties of thermoelectric CuAlO₂ ceramics aided by aluminosilicate glass

Improvement in electrical properties of thermoelectric CuAlO₂ ceramics aided by aluminosilicate glass