Half-Heusler Thermoelectric Material with Insulating Oxide Coat
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Solution Overview
Problem
Thermoelectric conversion materials face challenges in achieving high reliability and heat resistance, particularly in long-term use in high-temperature environments, due to the limitations of existing materials like PbTe alloys and the need for safer alternatives.
Innovation Solution
A thermoelectric conversion material with an MgAgAs type crystal structure, composed of elements such as Zr, Hf, Ni, Co, Sn, and Sb, is developed, with an insulating metallic oxide coat on its surface to enhance heat resistance and reliability, and a high-temperature brazing filler metal is used to join the material with electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PbTe alloy is used as thermoelectric conversion material, then good thermoelectric conversion performance is achieved, but harmful lead substances are present
Solution Approach 1:
The patent changes the material composition parameters by replacing PbTe alloy with half-Heusler compound having specific elemental composition (MgAgAs-type crystal structure with controlled ratios of main components), thereby eliminating lead while maintaining thermoelectric performance through compositional optimization
Solution Approach 2:
The patent employs composite material strategy by creating half-Heusler compound with multiple elements (Mg, Ag, As type crystal structure) to achieve both non-toxicity and high thermoelectric conversion efficiency, replacing the simpler PbTe alloy structure
2Power
If conventional thermoelectric materials are used in high-temperature environments, then power generation function is achieved, but heat resistance and reliability deteriorate over time
Solution Approach 1:
The patent optimizes the thermal and electrical parameters of the half-Heusler compound by controlling the ratio of main components and crystal structure characteristics, enabling the material to maintain stable thermoelectric performance and heat resistance in high-temperature power generation applications
Solution Approach 2:
The patent develops a thermoelectric material that can operate reliably in high-temperature environments for extended periods, replacing conventional materials that degrade quickly under thermal stress, thereby extending service life in power generation systems
3Reliability
If Seebeck coefficient is increased to improve conversion efficiency, then thermoelectric performance improves, but electrical resistivity and thermal conductivity become more challenging to optimize
Solution Approach 1:
The patent systematically adjusts the compositional parameters of the half-Heusler compound (elemental ratios, crystal structure parameters) to achieve optimal balance between Seebeck coefficient, electrical resistivity, and thermal conductivity, thereby maximizing the ZT value through controlled parameter variation
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
The solution significantly improves heat resistance and long-term reliability of thermoelectric conversion modules, enabling their use in high-temperature applications such as power generation systems and waste heat utilization without the harmful effects of lead-based materials.
Implementation Method 1
there has been an increasing interest in a thermoelectric generation device providing a power generation system using unused waste heat energy and using the Seebeck effect
Implementation Method 2
there has been an increasing interest in a thermoelectric cooling element using the Peltier effect as a CFC-free cooling device
Data Source
AI summary
A thermoelectric conversion material made of a polycrystalline material represented by a composition formula (1) shown below and having an MgAgAs type crystal structure is provided. An insulating coat is provided on at least one surface of the polycrystalline material. Composition formula (1): (Aa1Tib1)xDyX100-x-y, wherein 0.2≦a1≦0.7, 0.3≦b1≦0.8, a1+b1=1, 30≦x≦35, 30≦y≦35 hold, wherein A is at least one element selected from the group consisting of Zr and Hf, D is at least one element selected from the group consisting of Ni, Co, and Fe, and X is at least one element selected from the group consisting of Sn and Sb.