Precision grain Boundary Engineering in commercial Bi2Te2.7Se0.3 thermoelectric materials towards high performance

The evolution of grain boundary microstructures in gold thin films during annealing was investigated in order to find a clue to the development of high performance thin films by grain boundary engineering. The {111} oriented grains with the lowest surface energy were preferentially grown by surface energy-driven grain growth during annealing. The sharp {111} texture was developed by annealing at the temperature more than 873K. The remarkably high fraction of low-Σ coincidence site lattice (CSL) boundaries occurred when the area fraction of {111} texture increased to more than 95%. In particular, the fraction of some low-Σ CSL boundaries (Σ1,Σ3,Σ7) for the most sharply {111} textured specimen was found to be one order higher than those predicted for a random polycrystal. The utility of grain boundary engineering is discussed for controlling the performance degradation caused by the percolation phenomena of grain boundary diffusion in gold thin films.

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New Opportunities in Existing Thermoelectric Materials: Grain Boundary Engineering in Pulverized p-Bi2Te3 System

MRS Proceedings ◽

10.1557/proc-1044-u02-01 ◽

2007 ◽

Vol 1044 ◽

Author(s):

Jian He ◽

Xiaohua Ji ◽

Zhe Su ◽

Nick Gothard ◽

Justine Edwards ◽

...

Keyword(s):

Thermal Conductivity ◽

Grain Boundary ◽

Thermoelectric Materials ◽

Figure Of Merit ◽

Grain Boundary Engineering ◽

Nano Coating ◽

Compatibility Factor ◽

The Mean ◽

Mean Time ◽

Heterogeneous Layer

AbstractGrain boundary scattering provides an effective avenue to lower the thermal conductivity in polycrystalline thermoelectric materials, but it is hard to do this without simultaneously degrading the power factor that is the product of electrical conductivity and thermopower. An immediate question arises as to whether one can fabricate a thermoelectrically favorable grain boundary?In this paper we present a proof-of-principle grain boundary engineering study in the pulverized p-Bi2Te3 system. Utilizing the lately developed hydrothermal nano-coating technique, we fabricated an Alkali-metal(s)-containing surface layer with few tens of nm thick on the p-Bi2Te3 bulk reference grain, where it becomes part of the grain boundary upon hotpressing densification. The electrical resistivity, thermopower, thermal conductivity and Hall coefficient measurements constitute solid evidence that this heterogeneous layer helps decouple the otherwise inter-related resistivity, thermopower and thermal conductivity. To optimize the figure of merit ZT, we carefully varied the ratio between Na, K and Rb concentrations. It was found that the sample treated in the solution with Na/Rb =1:2 achieved a ZT comparable with that of the commercial ingot; in the mean time, the compatibility factor and robustness of device were considerably improved. In principle this technique can be applied to other existing polycrystalline thermoelectric materials as a new “tuning knob”.

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A New Approach to Grain Boundary Engineering for Photovoltaic Polysilicon by Unidirectional and Rotational Solidification

Materials Science Forum ◽

10.4028/www.scientific.net/msf.558-559.843 ◽

2007 ◽

Vol 558-559 ◽

pp. 843-850 ◽

Cited By ~ 5

Author(s):

Tadao Watanabe ◽

Kota Kido ◽

Sadahiro Tsurekawa ◽

Koichi Kawahara

Keyword(s):

Electrical Properties ◽

Grain Boundary ◽

High Performance ◽

Orientation Imaging Microscopy ◽

Basic Knowledge ◽

Grain Boundary Character Distribution ◽

Grain Boundary Engineering ◽

New Approach ◽

Boundary Density ◽

Boundary Microstructure

A new approach to grain boundary engineering for photovoltaic polysilicon has been attempted using a new processing method of unidirectional and rotational solidification from the melt, in order to control the grain boundary microstructure and to produce desirable bulk electrical properties. The effect of grain boundary microstructure on bulk electrical properties of polysilicon can be more precisely evaluated by introducing a new parameter “directional grain boundary density (DGBD)” in connection with basic knowledge of structure-dependent grain boundary electrical properties, the grain boundary character distribution (GBCD) and grain boundary geometrical configuration which can be experimentally determined by Orientation Imaging Microscopy (OIM). We report the usefulness of this approach to development of high performance polysilicon.

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Realizing high-performance thermoelectric power generation through grain boundary engineering of skutterudite-based nanocomposites

Nano Energy ◽

10.1016/j.nanoen.2017.10.003 ◽

2017 ◽

Vol 41 ◽

pp. 501-510 ◽

Cited By ~ 54

Author(s):

Qihao Zhang ◽

Zhenxing Zhou ◽

Maxwell Dylla ◽

Matthias T. Agne ◽

Yanzhong Pei ◽

...

Keyword(s):

Power Generation ◽

Grain Boundary ◽

Thermoelectric Power ◽

High Performance ◽

Grain Boundary Engineering ◽

Thermoelectric Power Generation

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Importance of Microscale Texture and Grain Boundary Connectivity to Percolation-Dependent Bulk Properties in Polycrystalline Materials

Materials Science Forum ◽

10.4028/www.scientific.net/msf.702-703.703 ◽

2011 ◽

Vol 702-703 ◽

pp. 703-709

Author(s):

Tadao Watanabe ◽

Shigeaki Kobayashi ◽

Xiang Zhao ◽

Liang Zuo

Keyword(s):

Grain Boundary ◽

High Performance ◽

Functional Materials ◽

Polycrystalline Materials ◽

Grain Boundary Character Distribution ◽

Grain Boundary Engineering ◽

Bulk Properties ◽

Close Relationship ◽

Boundary Microstructure ◽

Boundary Connectivity

Bulk properties of polycrystalline structural and functional materials are controlled by the grain boundary microstructure defined by the grain boundary character distribution (GBCD) and grain boundary connectivity, because of percolation-dependent grain boundary phenomena. It has been found that there is a close relationship between microscale texture and grain boundary microstructure. Since percolation-controlled grain boundary phenomena are involved and playing key roles in the generation of various kinds of bulk properties, the relationship between texture and grain boundary microstructure can be effectively used as a powerful tool in development of high performance structural and functional materials by Grain Boundary Engineering (GBE).

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A new approach to grain boundary engineering for nanocrystalline materials

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.7.176 ◽

2016 ◽

Vol 7 ◽

pp. 1829-1849 ◽

Cited By ~ 15

Author(s):

Shigeaki Kobayashi ◽

Sadahiro Tsurekawa ◽

Tadao Watanabe

Keyword(s):

Grain Boundary ◽

Fractal Analysis ◽

Nanocrystalline Materials ◽

High Performance ◽

Functional Materials ◽

Grain Boundary Character Distribution ◽

Grain Boundary Engineering ◽

Triple Junctions ◽

New Approach ◽

Boundary Connectivity

A new approach to grain boundary engineering (GBE) for high performance nanocrystalline materials, especially those produced by electrodeposition and sputtering, is discussed on the basis of some important findings from recently available results on GBE for nanocrystalline materials. In order to optimize their utility, the beneficial effects of grain boundary microstructures have been seriously considered according to the almost established approach to GBE. This approach has been increasingly recognized for the development of high performance nanocrystalline materials with an extremely high density of grain boundaries and triple junctions. The effectiveness of precisely controlled grain boundary microstructures (quantitatively characterized by the grain boundary character distribution (GBCD) and grain boundary connectivity associated with triple junctions) has been revealed for recent achievements in the enhancement of grain boundary strengthening, hardness, and the control of segregation-induced intergranular brittleness and intergranular fatigue fracture in electrodeposited nickel and nickel alloys with initial submicrometer-grained structure. A new approach to GBE based on fractal analysis of grain boundary connectivity is proposed to produce high performance nanocrystalline or submicrometer-grained materials with desirable mechanical properties such as enhanced fracture resistance. Finally, the potential power of GBE is demonstrated for high performance functional materials like gold thin films through precise control of electrical resistance based on the fractal analysis of the grain boundary microstructure.

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