Mg2SiSn Thermoelectric Junctions With Al Layers for 400°C Reliability
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Solution Overview
Problem
The challenge lies in creating a reliable thermoelectric conversion device using Mg2SiSn that can withstand temperatures up to 400°C, as existing methods like brazing at high temperatures often result in cracks and voids due to high junction temperatures and silver diffusion, making it difficult to commercialize devices for the 200-400°C medium temperature range.
Innovation Solution
A thermoelectric conversion element is developed using Mg2SiSn-based semiconductors with aluminum-based junction layers, where the Si content in the junction layers is adjusted to achieve a suitable junction temperature around 550-640°C, and alloy layers are formed to enhance reliability and prevent peeling, with Sn inclusion to suppress crack formation, and the use of Ni-based electrodes for high heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a general-purpose sintered mold is used for sintering thermoelectric materials, then the device complexity is reduced, but the manufacturing precision deteriorates due to inability to control oxygen partial pressure and atmosphere composition
Solution Approach 1:
The sintering system is segmented into distinct functional zones: a sintering chamber for thermal processing, a separate gas supply system with mass flow controllers for precise atmosphere control, and a pressure control system. This segmentation allows the mold structure to remain simple while achieving precise oxygen partial pressure control through dedicated control subsystems.
Solution Approach 2:
A gas supply system acts as an intermediary between the external environment and the sintering chamber, using mass flow controllers and pressure regulators to precisely control the oxygen partial pressure and atmosphere composition. This intermediary system enables precise control without complicating the fundamental sintering mold structure.
2Ease of manufacture
If conventional sintering methods are used, then the ease of manufacture is maintained, but the manufacturing precision deteriorates due to poor reproducibility of sintered body properties
Solution Approach 1:
The sintering system incorporates feedback control through sensors that monitor temperature, oxygen partial pressure, and atmosphere composition in real-time. These measurements are fed back to control systems that adjust gas flow rates and heating power to maintain setpoint conditions, ensuring reproducible sintered body properties while maintaining ease of manufacture through automated control.
Solution Approach 2:
Conventional mechanical atmosphere control methods are replaced with electronic control systems including mass flow controllers, pressure sensors, and computerized temperature control. This substitution maintains ease of manufacture through automated electronic control while dramatically improving the precision and reproducibility of sintering conditions.
3Power
If high-performance thermoelectric materials are produced with precise composition control, then the energy conversion efficiency is improved, but the manufacturing precision requirements increase the device complexity
Solution Approach 1:
The gas supply system is designed with multi-functionality, serving both to control oxygen partial pressure during sintering and to provide protective atmosphere during cooling. The same mass flow controllers and gas distribution system handle multiple atmospheric control requirements, reducing overall device complexity while enabling precise composition control for high-performance thermoelectric materials.
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 approach enables the production of thermoelectric conversion elements with high output and reliability, achieving a stable joined state that suppresses damage from heat and maintains performance across the desired temperature range.
Implementation Method 1
a sintered body sintered from a sintered compact is used as a thermoelectric converter
Implementation Method 2
When a temperature difference is applied between both ends of a conductor or semiconductor, an electromotive force (hereinafter referred to as Seebeck electromotive force) is generated in accordance with the Seebeck effect
Implementation Method 3
When a current is applied to a conductor or semiconductor, heat is absorbed or evolved in accordance with the Peltier effect
Data Source
Figure 1~2
Figure 3~3(b)
Figure 4~4(b)
AI summary
A thermoelectric conversion element (100) of the present invention includes a first electrode (105) which has one side joined to a first surface (101a) of an n-type semiconductor via an n-side junction layer (102), and the other side joined to a first surface (103a) of a p-type semiconductor via a p-side junction layer (104), and a second electrode (106) which is joined to each of a second surface (101b) of the n-type semiconductor and a second surface (103b) of the p-type semiconductor via the n-side junction layer (102) and the p-side junction layer (104). Each of the n-type semiconductor (101) and the p-type semiconductor (103) has a composition represented by Formulas (1) and (2) below, and the n-side junction layer (102) and the p-side junction layer (104) include Al. Mg2SiaSn1-a+A (1) MgmSixSnyGez+B (2)