Synthesis of NH4I-Doped Bi2Te3-Based Thermoelectric Materials in an Inert Gas Atmosphere Using an Automated System
Abstract
This article presents a comprehensive approach aimed at the full automation of the technology for producing semiconductor thermoelectric materials. The main stages of the technological chain—automatic dosing of high-purity raw materials in precise stoichiometric ratios. The combined use of vacuum at 10⁻³ Torr and an inert gas atmosphere (argon at 1.5 atm), holding at a temperature of 720 °C for 5–6 hours, crystal growth by the zone melting method and the cooling (annealing) regime—are analyzed as a single optimized process. The temperature–time profile, diffusion processes, and cooling dynamics are substantiated on the basis of physical models, including Fick’s law and Newton’s law of cooling. It is shown that real-time control of technological parameters using PLC controllers, SCADA systems, and artificial intelligence algorithms ensures phase homogeneity of the material, reduces defect density, and stabilizes electrophysical parameters. In ammonium iodide–doped Bi2Te3 thermoelement samples, the stability of electrical conductivity, the Seebeck coefficient, and the power factor along the entire sample length confirms the homogeneous distribution of dopant additives and the formation of a high-quality crystal structure. The obtained results demonstrate the high potential of the proposed automated technology for the effective application of Bi2Te3-based materials in low- and medium-temperature thermoelectric devices.
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