Protection against oxidation of tetrahedrite-based thermoelectric element

Tetrahedrite mineral family (Cu12Sb4S13), one of the most widespread sulfosalts on Earth's crust, seems to be an attractive sustainable source for p-type thermoelectric materials[1-3]. Unfortunately, beside phase decomposition with sulphur volatilization, oxidation of the tetrahedrite usually occurs in air atmosphere at its operating temperature range (RT- 450 °C)[4]. One way to overcome the problem of thermal degradation and consider tetrahedrite-based materials for practical devices operating in air atmosphere is material protection with oxidation-resistant thin films. In this work, an efficient protection against oxidative processes was obtained employing AlTiN based thin films. The coatings were deposited via reactive direct current physical vapour deposition magnetron sputtering. The composition, thermal and electrical behaviour of thin films were investigated by X-ray diffraction, energy dispersive spectroscopy associated to field emission scanning electron microscopy, thermogravimetric analyses, and electrical conductivity measurements. The barrier features for oxygen protection during thermal treatment in air at 500 °C were qualitatively evaluated, studying the coating behaviour over higher operating temperature of tetrahedrite based thermoelectric devices. [1]Battiston S, Fanciulli C, Fiameni S, Famengo A, Fasolin S, Fabrizio M. One step synthesis and sintering of Ni and Zn substituted tetrahedrite as thermoelectric material. J Alloys Compd 2017;702:75-83. doi:10.1016/j.jallcom.2017.01.187. [2]Fasolin S, Fiameni S, Fanciulli C, Battiston S, Famengo A, Fabrizio M. Nanostructured tetrahedrite synthesis for thermoelectric applications. J Nanosci Nanotechnol 2016;accepted:1645-9. doi:10.1166/jnn.2017.13733. [3]Lu X, Morelli DT. Natural mineral tetrahedrite as a direct source of thermoelectric materials. Phys Chem Chem Phys 2013;15:5762-6. doi:10.1039/c3cp50920f. [4]Gonçalves AP, Lopes EB, Montemor MF, Monnier J, Lenoir B. Oxidation Studies of Cu12Sb3.9Bi0.1S10Se3 Tetrahedrite. J Electron Mater 2018;47:2880-9. doi:10.1007/s11664-018-6141-9.