Thermal stability of Mg2Si0.55Sn0.45 for thermoelectric applications

Mahdi Mejri (1) , Benoît Malard (1) , Yohann Thimont (1) , Krunoslav Romanjek (2) , Hilaire Ihou Mouko , Claude Estournès (1)

1 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux
2 LITEN - Laboratoire d'Innovation pour les Technologies des Energies Nouvelles et les nanomatériaux

Understanding the thermal stability of the Mg2(Si,Sn) system is essential to define their safe tempera- tures of service. Despite its good thermoelectric performance, Mg2(Si,Sn) is subject to a phase separation during thermal cycling due to the miscibility gap, which leads to a degradation of its thermoelectric properties and affects its performance during device operation. Isothermal annealing at 500 !C and 750 !C were performed with different annealing time to investigate thermal stability of Mg2(Si,Sn). During the heat treatment, two phases were formed associated with porosity in the matrix. In addition, thickness of specimen was tracked and a significant expansion was detected. This phenomenon is attributed to the Kirkendall effect. The composition and the structure of the two forming phases were investigated by electron probe microanalysis and X-ray diffraction. Finally, the optimized thermal treatment allowed to stabilize the Mg2(Si,Sn) without porosity and the presence of two thermody- namically stabilized phase (Mg2Si0.41Sn0.59 and Mg2Si0.58Sn0.42) leading to a better reliability of the silicide thermoelectric modules.

Mots clés: Thermoelectric materials; Silicide Mg2(Si; Sn); Pesting; Thermal stability; Phase separation; Kirkendall effect; Porosity

Domaines: Matériaux

Mahdi Mejri, Benoît Malard, Yohann Thimont, Krunoslav Romanjek, Hilaire Ihou Mouko, et al.. Thermal stability of Mg2Si0.55Sn0.45 for thermoelectric applications. Journal of Alloys and Compounds, 2020, 846, pp.156413. ⟨10.1016/j.jallcom.2020.156413⟩. ⟨hal-03040584⟩