Chalcogen Compound Phase Stability Thermoelectric

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Solution Overview

Problem

Chalcogen-containing compounds with a face-centered cubic lattice structure, such as Sn4Bi2Se7, exhibit poor phase stability at low temperatures, limiting their application as thermoelectric conversion materials due to decomposition and poor thermoelectric properties.

Innovation Solution

A novel chalcogen-containing compound represented by the formula V1-2xSn4Bi2-xAg3xSe7, where 0<x<0.5, is developed, featuring a face-centered cubic lattice structure with vacancies and Ag substitution for Bi, enhancing phase stability and thermoelectric performance by optimizing the molar ratio of Bi:Ag to maintain a single phase and improve electrical conductivity and thermal conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If chalcogen-containing compounds with face-centered cubic lattice structure (such as Sn4Bi2Se7) are used to achieve low thermal conductivity through vacant lattice sites, then thermal conductivity is reduced, but phase stability deteriorates at low temperatures

Engineering Contradiction:

Improvephase stabilityVSAvoidthermoelectric performance

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent changes the compositional parameters by introducing Ag elements and adjusting the stoichiometric ratios (Sn4Bi2-xAgxSe7) to stabilize the face-centered cubic phase at low temperatures. This parameter modification allows the material to maintain its crystal structure and thermoelectric properties in the operating temperature range of 300-580K, resolving the phase stability issue while preserving low thermal conductivity.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite-like structure by incorporating Ag elements into the Sn-Bi-Se system, forming a multi-element chalcogenide compound. This composite approach combines the advantages of different elements: Sn and Bi provide the base structure with vacant sites for low thermal conductivity, while Ag enhances phase stability and electrical conductivity, achieving both reliability and performance.

Inventive Principle:

Principle #40Composite materials

2Reliability

If Ag is substituted for Bi in the compound structure to improve phase stability and electrical conductivity, then electrical conductivity increases, but the complexity of composition control increases

Engineering Contradiction:

Improveelectrical conductivityVSAvoidcomposition control

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent establishes specific parameter ranges for Ag substitution (0 < x ≤ 2 in Sn4Bi2-xAgxSe7) to optimize electrical conductivity while maintaining phase stability. By defining clear compositional boundaries and ratios, the patent simplifies the control process despite the multi-element complexity, making the material synthesizable with conventional techniques.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If the operating temperature is reduced to practical thermoelectric application range (300-580K), then application feasibility improves, but phase stability deteriorates due to decomposition

Engineering Contradiction:

Improveapplication feasibilityVSAvoidphase stability

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The patent modifies the compositional parameters by incorporating Ag elements which lower the phase transition temperature and stabilize the face-centered cubic structure at practical operating temperatures (300-580K). This allows the material to maintain its thermoelectric properties and crystal structure in the desired application temperature range, improving adaptability while ensuring stability.

Inventive Principle:

Principle #35Parameter changes

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 compound exhibits excellent phase stability at low temperatures, increased electrical conductivity, and improved thermoelectric performance, making it suitable for various thermoelectric applications, including cooling and power generation systems.

Implementation Method 1

research on thermoelectric conversion materials using waste heat as one of alternative energies has accelerated. The energy conversion efficiency of thermoelectric conversion materials depends on ZT, which is the thermoelectric performance index value... ZT=S2σT/K

Methodology Applied

Scientific EffectSeebeck effect: Seebeck Effect

Data Source

PatentUS11024438B2Chalcogen-containing compound, its preparation method and thermoelectric element comprising the same

Publication Date: 2021.06.01 LG CHEM LTD

AI summary

A chalcogen-containing compound of the following Chemical Formula 1 which exhibits excellent phase stability even at a low temperature, particularly at a temperature corresponding to an operating temperature of a thermoelectric element, and also exhibits a significantly superior power factor and thermoelectric performance index due to its excellent electrical conductivity and low thermal conductivity caused by its unique crystal lattice structure, a method for preparing the same, and a thermoelectric element including the same. [Chemical Formula 1]—V1-2xSn4Bi2-xAg3xSe7, wherein V is vacancy and 0<x<0.5.