Optimisation of the mechanochemical synthesis time of thermoelectric material Mg3Sb2–Mg3Bi2

Abstract

The present paper sets out the optimisation of the mechanochemical synthesis process of the thermoelectric material Mg_3.2Sb_1.5Bi_0.45Te_0.05. The current study investigates the effect of varying the time in the range from 1 to 9 hours on the phase composition, morphology of powders and thermoelectric properties of the samples obtained. It was established that the formation of the α-phase is complete after a period of 5 hours of mechanochemical synthesis. It was determined through the utilisation of scanning electron microscopy, in conjunction with an image analysis algorithm written in Python, that by 5 hours, a median particle size of 3.7 µm and the most uniform size distribution are achieved. It has been demonstrated that an increase in the duration to 7–9 hours results in particle agglomeration without any alteration to the phase composition. It was established that the specimen extracted from the powder following a period of 5 hours of mechanochemical synthesis possesses a thermoelectric figure of merit of zT ≈ 0.92 at 765 K. This investigation enabled the determination of the optimal time for the mechanochemical synthesis of the thermoelectric material Mg_3.2Sb_1.5Bi_0.45Te_0.05 through the utilisation of computer vision methodologies.