researchers from the university of houston (texas), as well as from universities across the u.s. and china and from the oak ridge national laboratory (oak ridge, tenn.), have developed a new mechanism that boost the performance of thermoelectric materials by increasing carrier mobility, how quickly charge-carrying electrons move across a material.

researchers enhanced thermoelectric materials by boosting carrier mobility.
(wikimedia commons)

according to a report from the university of houston, the researchers discovered an n-type magnesium-antimony material with a high thermoelectric figure of merit and enhanced the material’s power factor by tuning its carrier scattering.

“thermoelectric semiconductors come in two variations, n-type, created by replacing an element resulting in a ‘free’ electron to carry the charge, and p-type, in which the replacing element has one fewer electron than the element which it replaced, leaving a ‘hole’ that facilitates movement of energy as the electrons move across the material to fill the vacant spot,” the article explained.

it added, “the researchers replaced a small fraction of magnesium in the compound with a variety of transition-metal elements, including iron, cobalt, hafnium and tantalum, to determine how best to boost carrier mobility and, through that, the material’s power factor.”

researchers believe that this approach to thermoelectric materials could provide an enhancement to the many applications for this technology, including conversion of waste heat from power plants and other industries into electricity without generating additional greenhouse gases.

the research was recently published in proceedings of the national academy of sciences (pnas). the abstract stated:

“achieving higher carrier mobility plays a pivotal role for obtaining potentially high thermoelectric performance. in principle, the carrier mobility is governed by the band structure as well as by the carrier scattering mechanism. here, we demonstrate that by manipulating the carrier scattering mechanism in n-type mg₃sb₂-based materials, a substantial improvement in carrier mobility, and hence the power factor, can be achieved.

“{in this work, fe, co, hf, and ta are doped on the mg site of mg_3.2sb_1.5bi_0.49te_0.01, where the ionized impurity scattering crosses over to mixed ionized impurity and acoustic phonon scattering. a significant improvement in hall mobility from ∼16 to ∼81 cm²⋅v⁻¹⋅s⁻¹ is obtained, thus leading to a notably enhanced power factor of ∼13 μw⋅cm⁻¹⋅k⁻² from ∼5 μw⋅cm⁻¹⋅k⁻².

“a simultaneous reduction in thermal conductivity is also achieved. collectively, a figure of merit (zt) of ∼1.7 is obtained at 773 k in mg_3.1co_0.1sb_1.5bi_0.49te_0.01.

“the concept of manipulating the carrier scattering mechanism to improve the mobility should also be applicable to other material systems.”