Interfacial Stress Analysis on Skutterudite-based Thermoelectric Joints under Service Conditions

Xiao SHAO; Rui-Heng LIU; Liang WANG; Jing CHU; Guang-Hui BAI; Sheng-Qiang BAI; Ming GU; Li-Na ZHANG; Wei MA; Li-Dong CHEN

doi:10.15541/jim20190112

Journals >Journal of Inorganic Materials >Volume 35 >Issue 2 >Page 224 > Article

Journal of Inorganic Materials
Vol. 35, Issue 2, 224 (2020)

Interfacial Stress Analysis on Skutterudite-based Thermoelectric Joints under Service Conditions

Xiao SHAO^1、2, Rui-Heng LIU^1、3、*, Liang WANG¹, Jing CHU^1、2, Guang-Hui BAI⁴, Sheng-Qiang BAI^1、3, Ming GU¹, Li-Na ZHANG⁴, Wei MA⁴, and Li-Dong CHEN^1、3

Author Affiliations

¹The State Key Lab of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201899, China

²University of Chinese Academy of Sciences, Beijing 100049, China

³Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China

⁴Science and Technology on Space Physics Laboratory, Beijing 100076, China

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DOI: 10.15541/jim20190112 Cite this Article

Xiao SHAO, Rui-Heng LIU, Liang WANG, Jing CHU, Guang-Hui BAI, Sheng-Qiang BAI, Ming GU, Li-Na ZHANG, Wei MA, Li-Dong CHEN. Interfacial Stress Analysis on Skutterudite-based Thermoelectric Joints under Service Conditions[J]. Journal of Inorganic Materials, 2020, 35(2): 224 Copy Citation Text

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. (a) CTE, (b) Young’s modulus (E), and (c) variations of average first principle stresses with thicknesses of different DBL candidates (purple lines: CTE and E of SKD)

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σ1 distributions for (a) n=0, (b) n=1, (c) n=3, and (d) n=7 (initial thickness of Nb: 25 μm)

. σ₁ distributions for (a) n=0, (b) n=1, (c) n=3, and (d) n=7 (initial thickness of Nb: 25 μm)

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. Variations of average σ₁ on each interface with thicknesses of NbSb₂ and Nb

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$EDS mappings of (a, d) interfaces and (b, e) fracture surfaces of (a-b) unaged joint and (d-e) sample 650-10d (White line indicating the fracture surface, and white arrow indicating direction of observation in (b) or (d)); Total element data were shown in table (c) for figure (b) and in table (f) for figure (e)$

. EDS mappings of (a, d) interfaces and (b, e) fracture surfaces of (a-b) unaged joint and (d-e) sample 650-10d (White line indicating the fracture surface, and white arrow indicating direction of observation in (b) or (d)); Total element data were shown in table (c) for figure (b) and in table (f) for figure (e)

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. (a) Finite element model of SKD/Nb joint with pores, detailed meshes of (b) NbSb₂ layer and (c) CoSb₂ layer

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. Interface structures and line scans of joints

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. Relationships between interface stresses and pores major axis ratios

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. (a) Calculated stress state of SKD/Zr joint with the Zr layer of 25 μm and the micropores number n of 3; (b) Variation of average σ₁ on SKD/CoSb₂ interface with thickness of ZrSb₂ and Zr (n=3); (c) Variation of average σ₁ on CoSb₂/ZrSb₂ interface with thickness of ZrSb₂ and Zr (n=3); (d) Variation of average σ₁ on ZrSb₂/Zr interface with thickness of ZrSb₂ and Zr (n=3)

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Material	SKD	CoSb₂	NbSb₂^[1]	ZrSb₂^[2]	Nb	Zr
Molar Mass/(g·mol^-1)	424.21	302.45	336.43	334.82	92.91	91.22
Density/(g·cm^-3)	7.80*	8.36	8.29	7.62	8.57-8.45	6.5-6.4
Young’s modulus/GPa	120*	160	186.1	135.7	104.8-105.7	97-57
Poisson’s ratio	0.21^[3]	0.23	0.21	0.243	0.382-0.394	0.34
Thermal conductivity/(W·m^-1·K^-1)	3.04-4.05*	6.8-12.5^[4]	24	10	55-65	20-25
Thermal expansion/(×10^-6, K^-1)	10-11^[5]	14-23^[6]	8.4	9.7	7-7.8	5.9-6.9
Heat capacity/(J·g^-1·K^-1)	0.22-0.23*	0.247	0.222	0.223	0.27-0.45	0.28-0.34

Table 1.

Basic properties including molar mass, density, Young’s modulus, Poisson’s ratio, thermal conductivity, thermal expansions and heat capacity for series of materials

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Layer	SKD	Nb/Zr	CoSb₂	NbSb₂/ZrSb₂	Difference
Relative volume change (SKD/Nb)	-2.75	-0.27	+1.78	+1	-0.24
Relative volume change (SKD/Zr)	-2.48	-0.32	+1.65	+1	-0.15

Table 1.

Relative volume changes for one interface (SKD/Nb and SKD/Zr joints)

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Joints	d_NbSb2/μm	c/μm	n	Ave-σ₁/GPa	σ_t/MPa	Fracture position	Fracture composition
0 d	0	0	0	1.46	(9.68±1.70)	Nb/ SKD	(Nb+ NbSb₂)/(3%CoSb₂+97% SKD)
600-5 d	2	2.02	3	2.72	(4.63±2.12)	CoSb₂/NbSb₂	NbSb₂/(36%CoSb₂+64% SKD)
600-10 d	3	2.21	3	2.80	(3.39±1.44)	CoSb₂/NbSb₂	NbSb₂/(47%CoSb₂+53% SKD)
650-5 d	7	4.13	1	3.07	(4.44±1.50)	CoSb₂/NbSb₂	NbSb₂/(80%CoSb₂+20% SKD)
650-10 d	12	5.20	1	3.42	(1.46±0.38)	CoSb₂/NbSb₂	NbSb₂/(97%CoSb₂+3% SKD)

Table 2.

Thicknesses of NbSb₂ layer d_NbSb2, average sizes of micropores c, tensile strengths σ_t, maximum calculated stresses Ave-σ₁ and the location interfaces, compositions of tensile fracture surface for series of aging SKD/Nb joints。。

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