Chalcogen Compound Phase Stability Alkali Metal
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Solution Overview
Problem
Thermoelectric conversion materials with a face-centered cubic lattice structure, such as Sn4Bi2Se7, exhibit inferior phase stability at low temperatures, limiting their application in thermoelectric elements due to decomposition into other phases, despite their potential for low thermal conductivity and excellent electrical conductivity.
Innovation Solution
A chalcogen-containing compound with a face-centered cubic lattice structure, represented by Chemical Formula VxMyPbzSn4-zBi2Se7, is developed, where V is a vacancy, M is an alkali metal, and x, y, z are mole ratios that allow for partial vacancy filling by the alkali metal, enhancing phase stability and thermoelectric properties by optimizing the crystal structure and electron donation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a face-centered cubic lattice structure chalcogen compound (Sn4Bi2Se7) is used to achieve low thermal conductivity and excellent electrical conductivity, then thermoelectric conversion property is improved, but phase stability deteriorates at low temperatures
Solution Approach 1:
The patent changes the compositional parameters by introducing alkali metal elements (Li, Na, K) into specific lattice sites of the Sn4Bi2Se7 structure. This compositional modification allows the material to maintain the face-centered cubic lattice structure at lower temperatures while improving phase stability. The alkali metals occupy specific positions in the lattice, stabilizing the structure without eliminating the beneficial vacant lattice sites for low thermal conductivity.
Solution Approach 2:
The patent creates a composite structure by combining Sn4Bi2Se7 with alkali metal elements (forming compounds like A3Sn4Bi2Se7 where A is an alkali metal). This composite approach allows the material to inherit the excellent thermoelectric properties of the original compound while gaining enhanced phase stability from the alkali metal incorporation, resolving the contradiction between thermoelectric performance and stability.
2Reliability
If vacant lattice sites are maintained to achieve low thermal conductivity, then thermoelectric property is improved, but phase stability worsens due to decomposition at low temperatures
Solution Approach 1:
The patent applies local quality by selectively placing alkali metal atoms at specific lattice positions (such as the 4a site) while maintaining vacant sites at other positions (such as the 8c site). This localized modification allows the material to maintain low thermal conductivity through preserved vacant sites while gaining phase stability from the strategically positioned alkali metals that reinforce the lattice structure at critical locations.
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 achieves excellent phase stability at low temperatures, high electrical conductivity, and a high thermoelectric figure of merit (ZT) due to the unique crystal structure and electron donation, making it suitable for various thermoelectric applications.
Implementation Method 1
M is an alkali metal, and x, y, z are mole ratios that allow for partial vacancy filling by the alkali metal, enhancing phase stability and thermoelectric properties by optimizing the crystal structure and electron donation
Implementation Method 2
The energy conversion efficiency of such thermoelectric conversion material depends on a thermoelectric figure of merit (ZT). Here, ZT is determined according to the Seebeck coefficient, electrical conductivity, thermal conductivity, etc.
Data Source
AI summary
The present invention relates to a novel chalcogen-containing compound that exhibits excellent phase stability even at a temperature corresponding to the driving temperature of a thermoelectric element, and has a high output factor and thermoelectric figure of merit, a method for preparing the same, and a thermoelectric element including the same.