Grain Boundary Conductance Mechanisms of Ultra-fine Grained CeO2/BaCeO3 Based Electrolytes Fabricated by a Two-step Sintering Process

Abstract Aiming to clarify the grain boundary conductance mechanism of CeO2/BaCeO3 based electrolytes suitable for solid oxide fuel cells (SOFCs), Sm, Bi co-doping CeO2/BaCeO3 (80 wt.% Ce0.8Sm0.1Bi0.1O2-δ - 20 wt.% BaCe0.8Sm0.1Bi0.1O3-δ, BiSDC-BCSBi) electrolytes with ultra-fine grained (110-220 nm) and micron (1-1.8 μm) structures were prepared by the two step sintering and conventional sintering method, respectively. Both electrolytes have pure phases corresponding to CeO2 and BaCeO3 without other purities. In the ultra-fine grained structure, apparent grain boundary conductivities measured at 350 oC and 400 oC are 1-2 orders of magnitude higher than micron structures, thus resulting in dramatically enhanced electrical performances. This grain boundary effect can be attributed to two aspects. One is the decrease of space charge potential Δφ(0) (0.165 V for ultrafine-fine grained ones, 0.396 V for micron ones). The other is the dilution of impurities (the impurity blocking term ω/dg is 0.94 for ultrafine-fine grained ones, and 0.53 for micron ones). In the ultra-fine grained electrolytes, no extra electronic conduction is introduced, and the ion migration number of O2- is higher than that of H+. Finally, the ultra-fine grained BiSDC-BCSBi electrolytes maintain a good long-term stability in the operating condition of SOFCs at 600 oC for 100 h.

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Effect of Grain Size and Grain Boundary on Mechanical Yielding Behavior of Fully Stabilized Zirconia

Materials, Nondestructive Evaluation, and Pressure Vessels and Piping ◽

10.1115/imece2006-15418 ◽

2006 ◽

Author(s):

Jie Lian ◽

Javier Garay ◽

Junlan Wang

Keyword(s):

Mechanical Properties ◽

Grain Size ◽

Grain Boundary ◽

Boundary Effect ◽

Coarse Grained ◽

Stabilized Zirconia ◽

Fine Grained ◽

Grain Sizes ◽

Reduced Modulus ◽

Grain Boundary Effect

Mechanical properties of fully yttria stabilized zirconia (F-YSZ) with different grain sizes were investigated using instrumented indentation. While the grain size effect on the yield strength was performed on both the coarse-grained and fine-grained F-YSZ, the grain boundary effect was studied on the coarse-grained F-YSZ by performing nanoindentation within the grains and on/near the grain boundaries. Little variations were observed on mechanical properties such as hardness and reduced modulus, interesting results were obtained on the grain boundary effect on the yielding load for the course-grained F-YSZ.

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Superplasticity in NiAl and NiAl-based alloys

Journal of Materials Research ◽

10.1557/jmr.2002.0344 ◽

2002 ◽

Vol 17 (9) ◽

pp. 2346-2356 ◽

Cited By ~ 6

Author(s):

J. J. Guo ◽

X. X. Du ◽

L. L. Zhou ◽

B. D. Zhou ◽

Y. Y. Qi ◽

...

Keyword(s):

Grain Boundary ◽

Dynamic Recovery ◽

Columnar Structure ◽

Grain Boundary Sliding ◽

Dislocation Slip ◽

Directionally Solidified ◽

Superplastic Behavior ◽

Fine Grained ◽

Fine Grained Structure ◽

Boundary Sliding

Superplastic deformation was realized on NiAl and NiAl-based alloys prepared by both common casting and directional solidification. Directionally solidified NiAl–27Fe–3Nb alloy as well as conventionally cast NiAl, NiAl–25Cr, NiAl–9Mo, NiAl–20Fe–Y.Ce, and NiAl–30Fe–Y alloys exhibited typical deformation characteristics shown in conventionally superplastic materials. NiAl and NiAl-based alloys could be divided into three categories depending on their different superplastic behavior: finely grained structure (NiAl–9Mo, NiAl–25Cr, NiAl–20.4Fe–Y.Ce, NiAl–30Fe–Y), coarsely grained structure (NiAl), and columnar structure (NiAl–27Fe–3Nb). The corresponding deformation mechanisms for fine-grained structure, coarsely grained structure, and columnar structure were grain boundary sliding or grain boundary sliding accompanied by dynamic recrystallization, dynamic recovery and recrystallization, and intragrain dislocation slip, respectively.

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Control of Boundary Structure and Grain Growth for Microstructural Design

Materials Science Forum ◽

10.4028/www.scientific.net/msf.475-479.3891 ◽

2005 ◽

Vol 475-479 ◽

pp. 3891-3896 ◽

Cited By ~ 1

Author(s):

Si Young Choi ◽

Suk Joong L. Kang

Keyword(s):

Grain Boundary ◽

Grain Growth ◽

Grain Structure ◽

Boundary Structure ◽

Basic Principles ◽

Fine Grained ◽

Grain Boundary Structure ◽

Fine Grained Structure ◽

The Difference ◽

And Control

The design of microstructure in materials, ranging from ultrafine, moderately sized, duplex to single crystalline, has long been a challenging subject to material scientists. A basic means to achieve this goal is related to the control of grain growth. Taking BaTiO3 as a model system, this investigation shows that control of grain boundary structure between rough and faceted and control of initial grain size can allow us to achieve the goal. When the grain boundary is rough, normal grain growth occurs with a moderate rate. On the other hand, for faceted boundaries, either abnormal grain growth or grain growth inhibition occurs resulting in a duplex grain structure or fine-grained structure, respectively. Growth of single crystals is also possible when the boundary is faceted. During crystal growth amorphous films can form and thicken at dry grain boundaries above the eutectic temperature. As the film thickness increases, the growth rate of the crystals is reduced. This observed growth behavior of grains with boundary structure is explained in terms of the difference in mobility between the two types of boundaries. The results demonstrate the basic principles of obtaining various microstructures from the same material.

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