Key Takeaways & Executive Findings
- •• Simulation-assisted control of molten zone length improves tellurium purification efficiency. • COMSOL Multiphysics simulation accurately predicted molten zone length, validated by experiments. • Zone refining achieved >95% removal of Ca and Cu, and >70% removal of P from tellurium. • Final tellurium purity reached 6N under optimized conditions.
Abstract
The effect of temperature on molten zone length was investigated through simulation to optimize the control of molten zone length during the experimental process. The temperature gradient distribution within the molten zone during zone refining was simulated using COMSOL Multiphysics software and experimentally validated. The simulated molten zone length showed good agreement with the actual measured length. The experimental study of tellurium purification by zone refining was conducted under the following conditions: three passes of zone refining, a hydrogen flow rate of 0.5 L/min, and molten zone movement speeds of 0.5 and 1.0 mm/min. The results demonstrated that the removal efficiencies of impurities such as Ca and Cu exceeded 95%, while the removal efficiency of phosphorus (P) reached over 70%. And the purity of tellurium reached 6N.
1. Introduction
High-purity materials are essential for fundamental research and practical applications like semiconductor devices, infrared-detecting core components, and 5G communications. For example, Te with a purity of 5N is a crucial part of Bi2Te3-type alloys used to make power generators or thermoelectric coolers [1] and serves as a primary raw material for CdTe solar cells [2,3]. For tellurium in Cu2Te [4], HgTe, and HgCdTe [5] compounds, a purity of 6N−7N is required. These compounds are primarily used in devices such as spectral analyzers, infrared modulators, and nuclear radiation detectors. Although high-purity tellurium can be produced by a number of methods, zone refining is the most efficient method [6−8].
There are stringent requirements for the accurate regulation of temperature in the zone refining process [9−12]. The accurate control of the temperature zone in the zone refining process, and thus the control of the length of the molten zone, is currently a research hotspot. It has been well studied by researchers through simulation [13−15]. For example, LI et al [16] investigated the silicon purification process and demonstrated that the temperature distribution within the melt is influenced by both the number of induction heating sources and the position of the melt pool. By optimizing the numerical model through the input parameters, the temperature distribution and gradient in the silicon melt can meet the requirement of silicon vacuum induction refining. In the case of lanthanum purification, CHEN et al [17] employed the zone refining technique, establishing a simulation model using finite element analysis. And the results showed good agreement between the simulation and the experimental findings. ROUSSOPOULOS and RUBINI [18] explored the thermal field distribution of indium antimonide during the zone refining process and derived the correlation between the length of the molten zone and key parameters through process modeling.
At present, zone refining of tellurium is still poorly investigated, and a major challenge is the difficulty in effectively controlling the molten zone length during the refining process. Experimentally investigating the zone refining temperature and molten zone length is time-consuming and energy-intensive. These issues can be effectively addressed through numerical simulation combined with experimental verification [19−21]. To assist in selecting the temperature parameters, in this study, the molten zone length in the zone refining process was first simulated, and then validation experiments were conducted. Subsequently, tellurium purification tests using zone refining were performed based on the simulation results, and the purity and im
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Qing-hua TIAN, Zhi-qiang HE, Zhi-peng XU, Hai-bei WANG, Liu ZHU (2025). Preparation of high-purity tellurium based on simulation-assisted zone refining. SinoTechIntel Verified Research. https://doi.org/10.1016/S1003-6326(25)66987-1
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Frequently Asked Questions
What is the main objective of this study?
The main objective is to optimize the control of molten zone length during zone refining of tellurium using simulation, and to achieve high-purity tellurium (6N) through experimental validation.
How was the molten zone length simulated?
The molten zone length was simulated using COMSOL Multiphysics software, which modeled the temperature gradient distribution within the molten zone during zone refining.
What were the optimal zone refining conditions?
The optimal conditions were three passes of zone refining, a hydrogen flow rate of 0.5 L/min, and molten zone movement speeds of 0.5 and 1.0 mm/min.
What were the removal efficiencies for impurities?
The removal efficiencies for Ca and Cu exceeded 95%, while the removal efficiency for phosphorus (P) reached over 70%.
What final purity of tellurium was achieved?
The final purity of tellurium reached 6N (99.9999%).
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