Thermal Stability of Mg₂Si_0.6Sn_0.4 under Oxidation Conditions

Area of Science:

• Materials Science
• Solid State Chemistry
• Thermoelectrics

Background:

• Mid-temperature thermoelectric modules require materials with high oxidation resistance.
• Magnesium silicide-tin (Mg₂Si₀.₆Sn₀.₄) is a promising candidate for such applications.

Purpose of the Study:

• To evaluate the oxidation stability of Mg₂Si₀.₆Sn₀.₄ at mid-temperatures (400-600 °C) in air.
• To elucidate the degradation mechanism at higher temperatures.

Main Methods:

• Oxidation experiments under static and cyclic conditions at 400 °C.
• Thermogravimetry (TGA).
• Scanning electron microscopy (SEM).
• Temperature X-ray diffraction (T-XRD).
• Mechanical and thermodynamic analysis.

Main Results:

• Mg₂Si₀.₆Sn₀.₄ demonstrated excellent stability at 400 °C, enduring 100 hours of static exposure and 400 heating-cooling cycles.
• Material decomposition was observed above 500 °C in air.
• Degradation is attributed to the presence of tin and the formation of various oxides.

Conclusions:

• Mg₂Si₀.₆Sn₀.₄ is a stable and reliable thermoelectric material for mid-temperature applications up to 400 °C.
• Its use above 500 °C in air is limited due to oxidative decomposition mechanisms involving tin and oxide formation.