Hf-Doping Effect on the Thermoelectric Transport Properties of <i>n</i>-Type Cu<sub>0.01</sub>Bi<sub>2</sub>Te<sub>2.7</sub>Se<sub>0.3</sub>
oleh: Jeong Yun Hwang, Sura Choi, Sang-il Kim, Jae-Hong Lim, Soon-Mok Choi, Heesun Yang, Hyun-Sik Kim, Kyu Hyoung Lee
| Format: | Article |
|---|---|
| Diterbitkan: | MDPI AG 2020-07-01 |
Deskripsi
Polycrystalline bulks of Hf-doped Cu<sub>0.01</sub>Bi<sub>2</sub>Te<sub>2.7</sub>Se<sub>0.3</sub> are prepared via a conventional melt-solidification process and subsequent spark plasma sintering technology, and their thermoelectric performances are evaluated. To elucidate the effect of Hf-doping on the thermoelectric properties of <i>n</i>-type Cu<sub>0.01</sub>Bi<sub>2</sub>Te<sub>2.7</sub>Se<sub>0.3</sub>, electronic and thermal transport parameters are estimated from the measured data. An enlarged density-of-states effective mass (from ~0.92 <i>m</i><sub>0</sub> to ~1.24 <i>m</i><sub>0</sub>) is obtained due to the band modification, and the power factor is improved by Hf-doping benefitting from the increase in carrier concentration while retaining carrier mobility. Additionally, lattice thermal conductivity is reduced due to the intensified point defect phonon scattering that originated from the mass difference between Bi and Hf. Resultantly, a peak thermoelectric figure of merit <i>zT</i> of 0.83 is obtained at 320 K for Cu<sub>0.01</sub>Bi<sub>1.925</sub>Hf<sub>0.075</sub>Te<sub>2.7</sub>Se<sub>0.3</sub>, which is a ~12% enhancement compared to that of the pristine Cu<sub>0.01</sub>Bi<sub>2</sub>Te<sub>2.7</sub>Se<sub>0.3</sub>.