Thermoelectric Materials

Thermoelectric materials from mineral waste

Within the START project, developed an advanced p-type thermoelectric powder based on the tetrahedrite compound Cu₁₂₋ₓ(TM)ₓSb₄S₁₃ (TM = Fe, Zn). Tetrahedrites are copper-based sulfide minerals valued for their low thermal conductivity, use of earth-abundant and non-toxic elements, and strong potential in sustainable energy conversion. Through dual substitution of Cu with Fe and Zn, MBN’s material achieves optimised carrier concentration, delivering a thermoelectric figure of merit (ZT) > 1 with peak efficiency near 350 °C.

Produced via the proprietary Mechanomade® process, this zero-waste solid-state synthesis ensures homogeneous phases and precise control over composition. Consolidation by Spark Plasma Sintering (SPS) yields dense, fine-grained legs with high electrical conductivity, low thermal conductivity, and robust mechanical integrity.

COMPOSITION
Copper bal. – Antimony 30% – Sulphur 25% – Zinc 2% – Iron 1.7%

PROPERTIES
Seebeck coefficient               240–250 μV/K
Electrical resistivity                55–60 μΩ·m
Thermal conductivity             0.6 W/mK
ZT                                        1.1
Power factor                         1 mW/mK²

MBN has developed a high-performance n-type thermoelectric powder based on the Mg₃(Sb,Bi)₂ system. This class of materials represents one of the most promising tellurium-free alternatives for low- and mid-temperature thermoelectric applications, combining intrinsically low thermal conductivity with favourable electronic transport. Through optimised doping and partial substitution of Sb with Bi, MBN achieved enhanced carrier concentration and extended efficiency range, resulting in a peak ZT of 1.6 near 350 °C.

Synthesised via the proprietary Mechanomade® mechanosynthesis, the powder is uniformly mixed at the atomic scale, ensuring controlled phase formation and fine morphology. Spark Plasma Sintering (SPS) enables rapid densification while preserving the nanostructure that suppresses phonon transport. The resulting components combine high electrical conductivity, low thermal conductivity, and robust mechanical integrity for long-term operation in thermoelectric devices.

COMPOSITION
Magnesium bal. – Antimony 48% – Bismuth 28%

PROPERTIES
Seebeck coefficient      –230 to –240 μV/K
Electrical resistivity       30–35 μΩ·m
Thermal conductivity     0.8–0.9 W/mK
ZT                               1.2
Power factor                1.6 mW/mK²