Bulk PbTe-CdTe Nanocomposite Production via Rocking Bridgman Method
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Solution Overview
Problem
Current methods for producing PbTe-CdTe thermoelectric materials face challenges in achieving uniform distribution of CdTe precipitates and high thermoelectric efficiency due to limitations in solubility and structural defects, which restrict their application in broader temperature ranges and industrial uses.
Innovation Solution
A modified Bridgman method involving the mixing of elemental Lead, Tellurium, and Cadmium Telluride compounds at specific temperature ranges, followed by controlled solidification and rocking to ensure uniform CdTe distribution, reducing defects and enhancing thermoelectric properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rapid quenching or hot-pressing growth methods are used to produce Pb1-xCdxTe compounds with relatively high Cd content, then production time is reduced, but the material structure becomes defective with undesirable CdTe precipitation embedded in low Cd content Pb1-xCdxTe matrix
Solution Approach 1:
The patent applies preliminary action by pre-mixing elemental Pb, Te, and CdTe compounds in specific proportions before the growth process. This pre-preparation of input material ensures uniform distribution of CdTe throughout the PbTe matrix during subsequent solidification, preventing defective precipitation patterns that would otherwise require lengthy annealing to correct.
Solution Approach 2:
The patent utilizes parameter changes by controlling the melting temperature to be at least 30°C higher than the melting point of PbTe but at least 100°C lower than the melting point of CdTe, and maintaining this temperature for at least 48 hours. This specific temperature regime allows aggregation of CdTe into clusters rather than complete dissolution, achieving uniform distribution without requiring rapid quenching or extended annealing.
2Volume of stationary object
If conventional Bridgman method is used to obtain PbTe-CdTe nanocomposite, then bulk material can be produced, but uniform distribution of CdTe precipitates is not achieved
Solution Approach 1:
The patent applies preliminary action by pre-mixing elemental Pb, Te, and CdTe compounds in specific proportions before the growth process. This pre-preparation of input material ensures uniform distribution of CdTe throughout the PbTe matrix during subsequent solidification, preventing defective precipitation patterns that would otherwise require lengthy annealing to correct.
Solution Approach 2:
The patent applies periodic action by rocking the furnace with the dissolved material for at least 15 minutes with a frequency of 0.5 Hz. This periodic rocking motion during solidification promotes uniform distribution of CdTe precipitates throughout the bulk material, overcoming the limitation of conventional static Bridgman method.
3Reliability
If high Cd content is introduced into PbTe matrix, then thermoelectric efficiency is improved, but structural defects and non-uniform composition increase
Solution Approach 1:
The patent utilizes parameter changes by controlling the melting temperature to be at least 30°C higher than the melting point of PbTe but at least 100°C lower than the melting point of CdTe, and maintaining this temperature for at least 48 hours. This specific temperature regime allows aggregation of CdTe into clusters rather than complete dissolution, achieving uniform distribution without requiring rapid quenching or extended annealing.
Solution Approach 2:
The patent applies local quality by introducing CdTe in controlled amounts (2% to 10% of total molar mass) and allowing it to aggregate into clusters during controlled solidification. This creates local regions of enhanced CdTe concentration that improve thermoelectric efficiency while maintaining overall composition uniformity through the rocking process.
4Stability of the object's composition
If long-term annealing is performed to obtain single-phase Pb1-xCdxTe solid solution, then material homogeneity is improved, but production time increases significantly
Solution Approach 1:
The patent applies preliminary action by pre-mixing elemental Pb, Te, and CdTe compounds in specific proportions before the growth process. This pre-preparation of input material ensures uniform distribution of CdTe throughout the PbTe matrix during subsequent solidification, preventing defective precipitation patterns that would otherwise require lengthy annealing to correct.
Solution Approach 2:
The patent applies periodic action by rocking the furnace with the dissolved material for at least 15 minutes with a frequency of 0.5 Hz. This periodic rocking motion during solidification promotes uniform distribution of CdTe precipitates throughout the bulk material, achieving homogeneity without requiring long-term annealing.
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 method produces bulk PbTe-CdTe nanocomposites with improved thermoelectric performance, characterized by uniform CdTe distribution and reduced defects, leading to enhanced ZT values suitable for industrial applications across various temperature ranges.
Implementation Method 1
heating input material to temperature of at least 30°C higher than melting temperature of compound Lead Telluride PbTe but of at least 100°C lower than melting temperature of compound Cadmium Telluride CdTe
Implementation Method 2
solidifying the homogenized dissolved material for at least 3 hours in temperature lower than melting temperature of Lead Telluride by less than 100°C to obtain the nanocomposite PbTe-CdTe
Data Source
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AI summary
A method of production of bulk thermoelectric nanocomposite of Lead Telluride and Cadmium Telluride (PbTe-CdTe) by mixing compounds in temperature in which at least one compound is in a liquid form and subsequently solidifying, according to the invention is characterized in that it comprises step of preparation of an input material including mixing elemental Lead (Pb), elemental Tellurium (Te) and Cadmium telluride (CdTe) compound to obtain input material and placing input material in an ampoule. Lead (Pb) and Tellurium (Te) are provided in identical atomic proportion and mass of Cadmium Telluride (CdTe) compound is provided in range of 2% to 10% of total molar mass of input material. The method further comprises a step of heating input material to temperature higher than melting temperature of compound Lead Telluride (PbTe) but significantly lower than melting temperature of compound Cadmium Telluride (CdTe), during a time of at least 48 hours to obtain dissolved material. The method further comprises a step of rocking dissolved material for at least 15 minutes with frequency of 0.5 Hz. Invention further concerns a bulk nanocomposite of Lead Telluride and Cadmium Telluride obtained with the method according to the invention.