NbFeSb Half-Heusler Thermoelectric Materials with Sub-Micron Grains
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Solution Overview
Problem
Half-Heusler thermoelectric materials, such as MCoSb and MNiSn, have a lower dimensionless thermoelectric figure-of-merit (ZT) compared to state-of-the-art materials, limiting their thermoelectric performance, particularly due to high hafnium content costs and thermal conductivity issues.
Innovation Solution
Development of niobium (Nb), iron (Fe), and antimony (Sb) based nanocomposite half-Heusler thermoelectric materials with mean grain sizes less than one micron, achieved through melting, comminution, and consolidation processes, including substitution of niobium with titanium and antimony with tin, to enhance ZT values and reduce thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional half-Heusler materials (MCoSb, MNiSn) are used, then thermoelectric performance is limited by low ZT values, but material composition complexity and cost (particularly hafnium content) increase
Solution Approach 1:
The patent changes the compositional parameters by substituting conventional elements (Co, Ni, Hf, Zr) with alternative elements (Fe, Nb, Ti) to achieve high ZT values. Specifically, the formula Nb1-xTixFeSb1-yCoySnz modifies the stoichiometry and element composition to optimize thermoelectric performance while reducing complexity and cost.
Solution Approach 2:
The patent replaces expensive elements like hafnium and zirconium with cheaper alternatives such as niobium, titanium, and partial cobalt substitution. This reduces material cost while maintaining or improving thermoelectric performance through optimized composition ratios.
2Reliability
If grain size is reduced to increase ZT values, then thermoelectric performance improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes phase transition during consolidation by applying heat and pressure to transform nanometer-scale particles into a dense bulk material with controlled grain growth. This phase transition process enables achieving sub-micron grain sizes (less than one micron) while maintaining manufacturing feasibility.
Solution Approach 2:
The patent creates a nanocomposite structure by consolidating nanometer-scale particles into a bulk material with fine-grained microstructure. This composite approach combines the benefits of nanoscale grain boundaries (which scatter phonons and reduce thermal conductivity) with the mechanical strength of bulk material.
3Reliability
If nanometer scale particles are consolidated to form fine-grained material, then ZT values increase due to reduced thermal conductivity, but processing complexity increases
Solution Approach 1:
The patent segments the material into nanometer-scale particles through comminution before consolidation. This segmentation creates numerous grain boundaries that scatter phonons and reduce thermal conductivity, improving ZT values. The segmented structure is then consolidated into a bulk form with fine-grained microstructure.
Solution Approach 2:
The consolidation process utilizes phase transition from loose nanometer-scale particles to a dense bulk material under heat and pressure. This phase transition enables the formation of fine-grained microstructure with controlled grain sizes less than one micron, achieving reduced thermal conductivity while maintaining structural integrity.
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 peak ZT of about 1 at 700°C, comparable to high-performance p-type MCoSb materials, with improved thermoelectric performance and reduced material costs, while maintaining mechanical strength and thermal stability.
Implementation Method 1
The approach results in a peak ZT of about 1 at 700°C, comparable to high-performance p-type MCoSb materials, with improved thermoelectric performance and reduced material costs
Data Source
AI summary
A thermoelectric half-Heusler material comprising niobium (Nb), iron (Fe) and antimony (Sb) wherein the material comprises grains having a mean grain size less than one micron. A method of making a nanocomposite half-Heusler thermoelectric material includes melting constituent elements of the thermoelectric material to form an alloy of the thermoelectric material, comminuting (e.g., ball milling) the alloy of the thermoelectric material into nanometer scale mean size particles, and consolidating the nanometer size particles to form the half-Heusler thermoelectric material comprising at least niobium (Nb), iron (Fe) and antimony (Sb) and having grains with a mean grain size less than one micron.