Tellurium doped n-type Zintl Zr3Ni3Sb4 thermoelectric materials: Balance between carrier-scattering mechanism and bipolar effect

Abstract

Thermoelectric figure of merit ZT has been greatly improved in the past decade via band engineering to enhance power factor or nanostructuring to reduce thermal conductivity, but less attention has been paid to other significant factors, e.g., carrier scattering mechanism, bipolar effect, etc. Here we show that Te doping on the Sb site, as an n-type strong donor, could significantly suppress the high-temperature bipolar effect in the nanostructured Zintl Zr3Ni3Sb4, which can be ascribed to the combination of high majority-carrier concentration and enlarged band gap. A relatively good ZT of ∼0.6 at 773 K for Te doping can be achieved and that is almost double of the previous reported ZT by Cu doping. In addition, the role of carrier scattering mechanism on the low-temperature electrical transport properties is also pointed out, where both carrier mobility and power factor of Te doping, due to the detrimental effect of ionized impurity scattering, are lower than that of Cu doping in which the mixed acoustic phonon and ionized impurity scattering dominates.