Half-Heusler Thermoelectric Material with Multi-Phase Lattice Engineering
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Solution Overview
Problem
Conventional thermoelectric materials like Bi—Te and Pb—Te-based compounds contain toxic elements and do not exhibit sufficient ZT values, necessitating the development of non-toxic alternatives with improved thermoelectric conversion efficiency.
Innovation Solution
The use of half-Heusler compounds with a MgAgAs crystal phase, specifically compositions represented by formulas (A) and (B), which incorporate multiple crystal phases with varying lattice constants and optimized X-ray diffraction peak intensity ratios, along with heat treatment and element substitutions to enhance Seebeck coefficient, electrical resistivity, and thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Bi-Te-based or Pb-Te-based thermoelectric materials are used, then high thermoelectric conversion efficiency is achieved, but toxic elements are contained which are harmful to human bodies and the environment
Solution Approach 1:
The invention changes the compositional parameters by using half-Heusler compounds with specific atomic ratios (x=30-35, y=30-35) of non-toxic elements Ti, Zr, Hf, Ni, and Sn to achieve high ZT values without toxic Bi, Te, or Pb, directly resolving the contradiction between efficiency and toxicity
Solution Approach 2:
The invention creates composite thermoelectric materials by combining multiple half-Heusler compounds with different lattice constants in a specific intensity ratio (I1/(I1+I2)=0.2-0.8), achieving synergistic effects that provide both high conversion efficiency and non-toxicity
2Object-affected harmful factors
If conventional half-Heusler compounds with MgAgAs crystal phase are used, then non-toxic composition is achieved, but sufficient ZT values are not exhibited
Solution Approach 1:
The invention optimizes the lattice constant parameter by controlling the X-ray diffraction peak intensity ratio I1/(I1+I2) to be 0.2-0.8, which corresponds to specific atomic ratios in the half-Heusler compound, thereby achieving high ZT values while maintaining non-toxic composition
Solution Approach 2:
The invention introduces local structural variations by incorporating multiple MgAgAs crystal phases with different lattice constants in specific intensity ratios, creating localized regions with optimized properties that collectively achieve high thermoelectric performance
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
These materials achieve higher ZT values, particularly when the I1/(I1+I2) ratio is between 0.2 and 0.8, leading to improved thermoelectric performance and reduced toxicity, with optimal thermoelectric characteristics obtained through controlled heat treatment and element substitutions.
Implementation Method 1
thermoelectric generating devices making use of the Seebeck effect that can provide power generators using unused waste heat energy
Implementation Method 2
thermoelectric cooling devices making use of the Peltier effect
Implementation Method 3
assuming that X-ray diffraction peak intensity from a (422) diffraction plane of a first MgAgAs crystal phase having a smallest lattice constant and X-ray diffraction peak intensity from a (422) diffraction plane of a second MgAgAs crystal phase having a largest lattice constant be I1 and I2, respectively
Data Source
AI summary
A thermoelectric material includes a composition represented by the following formula (A): (Tia1Zrb1Hfc1)xNiySn100-x-y (A) where 0<a1<1, 0<b1<1, 0<c1<1, a1+b1+c1=1, 30≦̸x≦̸35, and 30≦̸y≦̸35. The composition includes at least two MgAgAs crystal phases different in a lattice constant, and, assuming that X-ray diffraction peak intensity from a (422) diffraction plane of a first MgAgAs crystal phase having a smallest lattice constant and X-ray diffraction peak intensity from a (422) diffraction plane of a second MgAgAs crystal phase having a largest lattice constant be I1 and I2, respectively, a value of I1/(I1+I2) is in a range of 0.2 to 0.8.