Phase boundary mapping and suppressing Pb vacancies for enhanced thermoelectric properties in n-type Sb doped PbTe compounds

Herein, the influence of Sb dopant on the thermoelectric properties of PbTe compound was systematically investigated by using a phase boundary method. Along different directions, the solubility limit of Sb in PbTe is distinct. Doping Sb in PbTe compounds generates cation vacancies in the structure. Due to the charge compensation of Pb vacancies in Sb containing PbTe, the solid solubility limit of Sb is significantly improved. The cation vacancies induced by Sb dopant dramatically impacts the thermoelectric performance. The presence of Pb vacancies in the lattice exerts long range coulombic force on the electron, which significantly decreases the carrier mobility. As a result, the power factor of Pb0.99Sb0.01Te sample is only 9.6 μW/cm/K2. Adding excessive Pb in Sb contained PbTe effectively inhibits the cation vacancies in the structure. This greatly improves the carrier mobility and overall electrical performance. PbSb0.01Te sample has the highest carrier mobility of ∼1,000 cm2/V/s. A large power factor of 19 μW/cm/K2 at room temperature and a maximum power factor of 28 μW/cm/K2 at 573 K are obtained. All these produce the highest ZT value of 1.22 at 773 K and the average ZT value of 0.7 in the temperature range of 298–823 K in Sb-containing PbTe through the defects design. This work provides a new avenue to further improve the thermoelectric properties of n-type PbTe-based thermoelectric materials.