Enhancement of figure of merit for Nernst effect in Bi77Sb23 alloy by Te-doping
Masayuki Murata, Kazuo Nagase, Kayo Aoyama, Atsushi Yamamoto
Abstract
The effect of carrier doping on the figure of merit for the Nernst effect zNernst is investigated using Bi77Sb23 alloys, aiming at the enhancement of the dimensionless figure of merit zNernstT at room temperature. Four Bi77Sb23 alloys—undoped, 0.1-, 0.2-, and 0.3-at.% Te-doped—are produced by spark plasma sintering and annealing. The Nernst thermopower, electrical resistivity, and thermal conductivity of undoped and Te-doped Bi77Sb23 alloys are measured in magnetic fields of up to 6 T at temperatures from 10 K to 300 K to determine zNernstT. The magnitude of the Nernst thermopower increases by 102% at 300 K because of the modification of the electron and hole carrier mobility by 0.1-at.% Te-doping. In addition, the magnetoresistance effect is suppressed over the entire temperature range owing to the fact that charge neutrality is destroyed by Te-doping, and this contributes to the enhancement of zNernstT. The thermal conductivity in the magnetic field is increased by Te-doping due to the increased electron thermal conductivity. Thus, zNernstT for the Bi77Sb23 alloy at 300 K is increased by 329% as a result of 0.1-at.% Te-doping.