Manipulation of ionized impurity scattering for achieving high thermoelectric performance in n-type Mg3Sb2-based materials

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 Mg3.2Sb1.5Bi0.49Te0.01, where the ionized impurity scattering crosses over to mixed ionized impurity and acoustic phonon scattering. A significant improvement in Hallmobility from similar to 16 to similar to 81 cm(2).V-1.s(-1) is obtained, thus leading to a notably enhanced power factor of similar to 13 mu W.cm(-1).K-2 from similar to 5 mu W.cm(-1).K-2. A simultaneous reduction in thermal conductivity is also achieved. Collectively, a figure of merit (ZT) of similar to 1.7 is obtained at 773 K in Mg3.1Co0.1Sb1.5Bi0.49Te0.01. The concept of manipulating the carrier scattering mechanism to improve the mobility should also be applicable to other material systems.