Thermoelectric Material Grain Boundary Composition for ZT Optimization
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Solution Overview
Problem
Current thermoelectric conversion materials have limited efficiency in converting temperature differences into electric energy, as indicated by a low ZT value, which restricts their ability to achieve high electric conductivity and thus hinder improved thermoelectric conversion efficiency.
Innovation Solution
A thermoelectric conversion material composed of a compound semiconductor with an amorphous phase and crystal phases having an average grain size of more than 5 nm, where the specific base material element's atomic concentration in the crystal phases is higher than in the compound semiconductor, enhancing electric conductivity and increasing the ZT value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thermoelectric conversion materials are used, then the material structure is simple, but the ZT value is low and electric conductivity is insufficient
Solution Approach 1:
The patent employs composite materials by combining amorphous phase and crystal phases within a single thermoelectric conversion material. The amorphous phase provides low thermal conductivity while the crystal phases contribute high electric conductivity, creating a composite structure that achieves high ZT value (greater than 1.5) without requiring multiple separate material layers or complex device architectures.
Solution Approach 2:
The patent applies local quality by creating regions with different phases and compositions within the material. The amorphous regions provide thermal insulation while crystal regions provide electrical conduction pathways. Additionally, the specific base material element is concentrated in crystal phases at higher atomic concentrations than in the bulk compound semiconductor, optimizing local electronic properties to enhance overall thermoelectric performance.
2Reliability
If the atomic concentration of specific base material element is increased in crystal phases, then electric conductivity increases and ZT value increases, but the compositional control becomes more difficult
Solution Approach 1:
The patent utilizes parameter changes by controlling the atomic concentration of the specific base material element to be higher in crystal phases than in the bulk compound semiconductor (difference of at least 3 at%). This compositional parameter optimization, combined with controlling crystal phase grain size (5-50 nm), creates the necessary conditions for high electric conductivity and ZT value while providing clear manufacturing targets for compositional control.
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 proposed material design significantly improves thermoelectric conversion efficiency by increasing electric conductivity and ZT value, while maintaining thermal conductivity and Seebeck coefficient within optimal ranges, leading to enhanced power generation capabilities.
Implementation Method 1
heat is directly converted into electric power... ZT equals to α2ST/K, where a represents a Seebeck coefficient, S represents an electric conductivity
Data Source
AI summary
A thermoelectric conversion material is composed of a compound semiconductor including a plurality of base material elements, and includes: an amorphous phase; and crystal phases having an average grain size of more than or equal to 5 nm, each of the crystal phases being in a form of a grain. The plurality of base material elements include a specific base material element that causes an increase of a band gap by increasing a concentration of the specific base material element. An atomic concentration of the specific base material element included in the crystal phases with respect to a whole of the plurality of base material elements included in the crystal phases is higher than an atomic concentration of the specific base material element included in the compound semiconductor with respect to a whole of the plurality of base material elements included in the compound semiconductor.