Half-Heusler Alloy Phase Separation for Thermal Conductivity Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current half-Heusler alloys used in thermoelectric generators have high thermal conductivity, limiting their efficiency in converting waste heat into electricity, as they are good conductors of both electricity and heat, and there is no established method to reduce thermal conductivity while maintaining electrical conductivity.
Innovation Solution
Introducing a secondary immiscible phase with a disordered structure into the half-Heusler alloy to scatter phonons and reduce thermal conductivity without impeding electrical conductivity, achieved through partial substitution of elements and synthesis of immiscible phases with specific stoichiometry and microstructuring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If half-Heusler alloys are used as thermoelectric materials, then good electrical conductivity is achieved, but high thermal conductivity limits efficiency
Solution Approach 1:
The patent creates a composite material system consisting of a half-Heusler matrix phase combined with a secondary immiscible phase (such as Laves phase, sigma phase, or topologically protected phase). This composite structure allows the material to simultaneously achieve low thermal conductivity through phonon scattering at phase boundaries while maintaining good electrical conductivity through the metallic half-Heusler matrix, thereby resolving the contradiction between reducing thermal conductivity and maintaining electrical conductivity for improved thermoelectric efficiency
Solution Approach 2:
The invention introduces local structural variations by creating discrete secondary phases with specific compositions and structures distributed within the half-Heusler matrix. These localized regions provide strong phonon scattering centers that reduce thermal conductivity, while the surrounding half-Heusler matrix maintains its excellent electrical conductivity properties, achieving local optimization of thermal and electrical transport properties
2Loss of energy
If regular lattice structure is used, then good electrical conductivity is achieved, but heat is also conducted efficiently
Solution Approach 1:
The patent utilizes phase separation to create a two-phase microstructure where the half-Heusler phase provides electrical conductivity and the secondary immiscible phase provides thermal insulation. The phase boundaries act as interfaces that scatter phonons (heat carriers) more effectively than electrons, thereby reducing heat conduction while preserving electrical conductivity through the metallic half-Heusler regions
3Loss of energy
If individual atoms are trapped in crystalline cage structures, then thermal conductivity is reduced, but this does not impede electrical conductivity
Solution Approach 1:
Instead of trapping individual atoms in crystalline cages, the patent segments the material into distinct phases with different compositions and structures. The secondary immiscible phase forms discrete regions (particles, domains, or layers) distributed within the half-Heusler matrix, creating a segmented microstructure that provides extensive phonon scattering interfaces while maintaining the overall metallic character and electrical conductivity of the half-Heusler phase
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 approach results in a material with significantly reduced thermal conductivity below 4 W/mK while maintaining high electrical conductivity and thermal voltage, enhancing the efficiency of thermoelectric generators for waste heat utilization.
Implementation Method 1
Introducing a secondary immiscible phase with a disordered structure into the half-Heusler alloy to scatter phonons and reduce thermal conductivity without impeding electrical conductivity
Implementation Method 2
Thermoelectric materials generate an electrical voltage when subjected to a temperature gradient. This is used in thermoelectric generators to produce electrical energy.
Data Source
Figure 1
Figure 2~3
AI summary
An inorganic, intermetallic compound is characterized in that the compound contains at least two elements per formula unit and consists of at least two phases, where at least one phase is semiconducting or semimetallic, and these at least two phases are immiscible with one another and thermodynamically stable. The invention allows the thermal conductivity of semi-Heusler alloys to be reduced while at the same time retaining the electrical conductivity and the thermal stress.