Transition of p- to n-Type Conductivity in Mechanically Activated Bismuth Telluride

Abstract

Bismuth telluride (Bi 2 Te 3 ) exhibits a transition from p-to n-type conduction as a result of high-energy ball milling. The transition is monitored over mechanical activation through measurement of the thermoelectric properties in the temperature range of 1.9 K to 390 K. Data show a flip in polarity of the Seebeck coefficient from 225 lV K À1 for the bulk sample to À 120 lV K À1 (at 315 K) that correlates to fracturing the layered-like structure of stoichiometric Bi 2 Te 3 into platelets and fine particles. The electronic transition is generated by fracturing the crystal 90°to the basal plane. This is the structural equivalent to inducing n-type, anti-site defects on grain boundaries. The observed phenomenon could be exploited to fabricate p-and n-type legs for thermoelectric devices from the same material. In this report, we demonstrate that the value of the Seebeck coefficient for bismuth telluride can be tuned using mechanical treatment. We also determine how mechanical activation of Bi 2 Te 3 impacts physical properties of the system, including: particle size, crystal structure, band gap, electrical and thermal conductivity, carrier concentration and mobility, average hopping distance, and the concentration of localized charged centers.

Superior energy density through tailored dopant strategies in multilayer ceramic capacitors

“…The positive S for x r 0.02 indicates p-type conduction but the magnitude of S becomes smaller as x increases, presumably due to a decrease in n. 52 For x Z 0.03, S changes from positive to mixed negative and positive as a function of temperature, indicating a shift from p-to n-type conduction. 53 Typical Z* plots and combined Z 00 and M 00 spectroscopic plots at 703 K of BF-ST-BMN-xNb ceramics are provided in Fig. S3a and b (ESI †).…”

Synergistic effect of Zn doping on thermoelectric properties to realize a high figure-of-merit and conversion efficiency in Bi2−xZnxTe3 based thermoelectric generators

“…4(a)). Undoped Bi 2 Te 3 attains a max of À160 mV K À1 at 400 K, slightly higher than the value reported by Martirosyan et al 31 Above 400 K, a decreases with increasing temperature, attributed to the onset of intrinsic conduction in the sample due to the thermal excitation. A similar parabolic trend of a is also observed in Bi 2Àx Zn x Te 3 (0.1 r x r 0.3) samples, in addition to the shift of the onset temperature for bipolar conduction towards the higher side.…”

High-energy laser detection through thermoelectric generators

“…Variation in effective Seebeck coefficients can be wide even among nominally the same materials based on processing conditions and with variation due to temperature. 19 For simplicity, the n-and p-type materials were assumed to have exactly opposite Seebeck coefficients. The terminal ohmic contacts were designated as either ground or a terminal by which to measure the simulated open-circuit voltage response of the TEG.…”