Manganese telluride - What is it? How does it work?

Manganese telluride introduction

CAS: 12032-89-2

EINECS No.: 234-782-1

Molecular Formula: MnTe

Safety Instructions: Reacts violently with lithium when heated to 230°C. When heated to decomposition it emits toxic fumes of Te. See also TELLURIUM and MANGANESE COMPOUNDS.

Manganese powder properties

Melting point: 1177°C

Density: 6.000

Form: Lumps

Color: dark gray

Water solubility: Insoluble.

Stable at room temperature and pressure Materials to avoid Alkali metals. For NiAs structure, the heat of formation is -111.3kJ/mol

Manganese telluride granules application

Manganese telluride (MnTe) is a hot material. The quasi-reluctance in Manganese telluride (MnTe) extends to very high temperatures and produces a thermoelectric potential much stronger than that generated by electron charges alone. Thermoelectric materials convert heat directly into electricity without emitting toxic gases or requiring moving parts. It offers a practical solution to the increasingly serious energy crisis and environmental problems. In recent years, lead-free manganese telluride (MnTe), which is composed of non-toxic, environmentally friendly and abundant elements, has attracted more and more attention. 

The direct band gap of MnTe with hexagonal NiAs structure is 1.27 eV and the indirect band gap is 0.81 eV. The high symmetry structure of MnTe leads to its high Seebeck coefficient. The high Seebeck coefficient and relatively low thermal conductivity indicate that MnTe is a promising medium temperature thermoelectric material. However, the strong optical phonon scattering due to the large electronegativity difference between Mn (1.55) and Te (2.10) reduces the carrier mobility. Low carrier mobility and low carrier concentration (1018 cm-3) make MnTe's electrical performance unsatisfactory. 

At present, there are many reports on improving electric transport performance by optimizing carrier concentration. For example, doping of Cu, Ag and Na at Mn site can effectively increase the carrier concentration and lead to the enhancement of the power factor. However, the thermoelectric value of MnTe is still at a low level. In order to match conventional N-type products to form efficient thermoelectric devices, P-type MnTe still needs to optimize its electrothermal transport performance to obtain higher ZT. In general, increasing the conductivity by doping will cause the Seebeck coefficient of the material to decrease greatly due to the increase of the carrier concentration.

Recently, Professor Tang Guodong of Nanjing University of Science and Technology cooperated with researcher Zhang Yongsheng of the Institute of Solid State Studies of the Chinese Academy of Sciences and others to obtain MnTe-based thermoelectric materials with ultra-high thermoelectric performance through SnTe nanocrystals and manipulating the energy band structure. The team found that the introduction of SnTe makes the electronic structure of MnTe undergo high-energy band convergence, resulting in a significant enhancement of the Seebeck coefficient. 

Compared with the previously reported doped MnTe, the Seebeck coefficient is greatly improved. Meanwhile, the introduction of SnTe can improve the carrier concentration. The larger Seebeck coefficient combined with the increased conductivity yields a high power factor of about 1230 μWm-1K-2. In addition, SnTe nanocrystals facilitate efficient phonon scattering, resulting in a significant reduction in lattice thermal conductivity. The proposed new strategy decouples the electronic and phonon transport of MnTe, enabling the Mn1.06Te-2% SnTe material to achieve a high ZT level of 1.4 at 873 K. The findings promote MnTe-based materials as strong candidates for waste heat recovery at intermediate temperatures.