Effect of spraying power on the microstructure and thermoelectric performance of plasma sprayed higher manganese silicides films

Higher manganese silicides (HMS) are deemed as particularly promising p-type thermoelectric materials. Apart from considerations in the materials available, the difficulty in converting them into engineering devices also limits thermoelectric applications. Atmospheric plasma spraying, as a flexible and cost-effective manufacturing process, was employed to produce thermoelectric films. In this study, HMS films were deposited using atmospheric plasma spray under controlled spraying power with different thermal exposures. The as-sprayed HMS films were characterized not only for phase and microstructure, but also for temperature dependent electrical conductivity and Seebeck coefficient. The power factor was calculated to assess the effect of spraying power on thermoelectric performance. The results show that the spraying power not only affects the melt state of the HMS particles, which leads to the variation of the microstructure of the films, but also its stoichiometry associated with phase transformation during spraying process. The maximum power factor value of 156.90 μW m ⁻¹ K ⁻² was acquired at 500 °C for HMS film deposited with the lowest spraying power. The results provide a large-scale fabrication method to improve the potential applicability of thermoelectric films.