Thermoelectric properties of Hf<inf>1&#x2212;x</inf>Zr<inf>x</inf>Te<inf>5</inf> polycrystals with high density

Strong Anisotropy and Bipolar Conduction-Dominated Thermoelectric Transport Properties in the Polycrystalline Topological Phase of ZrTe5

“…Specifically, as the temperature increases from low temperature to room temperature, the induced lattice expansion and the increase in interlayer distance lead to topological phase transitions from the STI to the DSM and then to the WTI, as schematically illustrated in Figure a. This discovery unified the differences in the electronic band structure of ZrTe 5 that were reported by various groups, − and well explained the temperature-dependent and magnetic field-dominated transport characteristics of doped samples. , Moreover, Zhang et al also found by ARPES that ZrTe 5 features a temperature-induced Lifshitz electronic transition, in which the Fermi level ( E F ) will move toward the valence band as temperature increases, as illustrated in Figure a.…”

“…The energy conversion efficiency of TE materials is determined by the TE dimensionless figure of merit ZT , ZT = S 2 T /ρ­(κ e + κ L ), where S is the Seebeck coefficient, ρ is the electrical resistivity, T is the absolute temperature, κ e is the electronic thermal conductivity, and κ L is the lattice thermal conductivity of the materials. − The high conversion efficiency requires a high power factor (PF = S 2 /ρ) and low thermal conductivity in TE materials. The thermal conductivity of ZrTe 5 is very low, for example, the κ L of its single crystal along the b axis is as low as 0.35 W m –1 K –1 , which makes this material a potential candidate with significant TE performances. − The reasons for its low κ L include its heavy element content, complex crystal structure, van der Waals (vdW) layered structure, and weak chemical bonds …”

“…The thermal conductivity of ZrTe 5 is very low, for example, the κ L of its single crystal along the b axis is as low as 0.35 W m −1 K −1 , 9 which makes this material a potential candidate with significant TE performances. 10− 14 The reasons for its low κ L include its heavy element content, complex crystal structure, van der Waals (vdW) layered structure, and weak chemical bonds. 15 Density functional theory calculations have showed that a small change in the lattice constant of ZrTe 5 would cause topological phase transitions from a strong topological insulator (STI) to a three-dimensional Dirac semimetal (DSM) and to a weak topological insulator (WTI).…”