Thermoelectric Element Buffer Layer Design for Stress Management
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Solution Overview
Problem
Existing thermoelectric elements face challenges in reducing dimensions while maintaining reliable operation under significant temperature differences due to thermomechanical stresses and chemical diffusion issues, limiting their performance and practical applications.
Innovation Solution
A thermoelectric converter design featuring a central layer of N- or P-type thermoelectric material with intermediate diffusion barrier layers and composite metallic buffer layers, where the combined thickness of the buffer layers is significantly greater than the central layer, made from alloys like Ti x Ag1-x, V x Fe1-x, to absorb mechanical stresses and prevent diffusion, along with a solder layer for secure electrode connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the dimensions of thermoelectric elements are reduced to increase electrical power density, then power density is improved, but thermomechanical stresses cause irreversible damage and reliability deteriorates
Solution Approach 1:
The patent introduces a buffer layer of composite metallic material between the thermoelectric layer and the electrodes. This intermediary layer absorbs thermomechanical stresses that would otherwise cause cracks in the thermoelectric material, thereby maintaining reliability while allowing reduced dimensions for higher power density.
Solution Approach 2:
The buffer layer is made of composite metallic material with specific composition (containing at least one metal from Ag, Al, Au, Cu, Fe, Ni, Pd, Pt, and at least one metal from Ti, V, Cr, Mn, Co, Zn, Ga, Ge, In, Sn, Sb, Te, Bi) and controlled thickness (5-50 μm). This composite structure provides both mechanical stress absorption and chemical diffusion barrier properties.
2Power
If the dimensions of thermoelectric elements are reduced, then electrical power density is increased, but chemical diffusion between thermoelectric legs and electrodes intensifies causing degradation
Solution Approach 1:
The buffer layer serves as a chemical intermediary between the thermoelectric layer and electrodes, preventing direct contact and thus stopping chemical diffusion. This maintains compositional stability while allowing the thermoelectric elements to operate at higher power densities with reduced dimensions.
Solution Approach 2:
The buffer layer acts as a physical barrier that prevents interdiffusion of atoms between the thermoelectric material and electrode materials, thereby preserving the chemical integrity and electrical properties of the junction over time.
3Ease of manufacture
If thermoelectric materials in massive form are used, then manufacturing flexibility is improved, but mechanical fragility increases leading to cracks under thermomechanical stress
Solution Approach 1:
The patent uses composite metallic material for the buffer layer, combining multiple metals to achieve both mechanical strength and compatibility with the thermoelectric material. This composite approach maintains ease of manufacture through powder metallurgy while providing the necessary mechanical strength to prevent cracks.
Solution Approach 2:
The buffer layer acts as a mechanical intermediary that absorbs and distributes thermomechanical stresses, preventing stress concentration that would lead to cracks in the massive form thermoelectric material, thereby maintaining both manufacturability and strength.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances the reliability and performance of thermoelectric converters, allowing for higher power density and improved thermal stability, with reduced material usage and lower contact resistances, enabling operation over a broader temperature range.
Implementation Method 1
an intermediate layer forming a barrier of diffusion
Implementation Method 2
the thermomechanical stresses cause irreversible damage (cracks) in particular in the vicinity of the interface with the metal electrodes
Implementation Method 3
the constituent material of the buffer layers is an alloy of two metals chosen from the family: TixAg1-x, VxFe1-x, Vx Ag1-x, TixFe1-x
Implementation Method 4
thermoelectric converters and thermoelectric elements used to produce such converters. Converters or thermoelectric devices make it possible to produce 'cold' (refrigeration/air conditioning applications) but also to recover thermal effluents to elegantly produce electricity.
Implementation Method 5
a solder layer, the thickness of which is between 10 μm and 500 μm
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a thermoelectric element, which is especially for a thermoelectric converter, including an assembly of constituent layers comprising a central layer made of p- or n-type thermoelectric material, then, in an assembly direction, and on each side of said central layer, an intermediate layer forming a diffusion barrier followed by a buffer layer made of composite metal material, said buffer layers being intended to be securely fastened to metal electrodes, characterised in that the cumulative thickness of the two buffer layers is larger than or equal to 50% of the thickness of the central layer, and preferably larger than or equal to 100% of the thickness of the central layer and very preferably larger than or equal to 200% of the thickness of the central layer, and in that the constituent material of the buffer layers is an alloy of two metals chosen from the family: Tix Ag1-x, Vx Fe1-x, Vx Ag1-x, Tix Fe1-x, where 0 < x < 1.