Fluorine doping for improved thermoelectric properties of spark plasma sintered bismuth telluride

摘要

Bismuth-telluride(Bi_(2)Te_(3))is considered to have the best thermoelectric properties at room temperature(ca.300 K).Thus,synthesis and improvement of Bi_(2)Te_(3)and its derivatives quickly and cost-effectively at favorite temperatures are of interests.Recently,doping fluorine(F)into electronic materials(e.g.,FTO)has gained attention;however,it is not applied to Bi_(2)Te_(3)till now.Here,our synthesis of F-doped Bi_(2)Te_(3)for thermoelectric application is introduced using spark plasma sintering(SPS)for Bi_(2)Te_(3)preparation and reactive ion etching(RIE,with SF_6 gas)for F-doping.The exposure time of SF_6 plasma is adjusted to evaluate F-doping effect on the thermoelectric properties of the samples.During characterizations,the increased electrical conductivity and the improved Seebeck coefficient of F-doped Bi_(2)Te_(3)are observed.Through spectroscopic studies and DFT calculations,the main mechanism behind that improvement is unveiled.It also emphasizes the essential role of the F-doping(optimum treatment time of 40 s)in increasing the carrier concentrations as well as electrical conductivity.With increasing measurement temperature(300-510 K),F-doping raises the figure of merit of electron rich Bi_(2)Te_(3)from 1.0 to 1.11(peaked at 390 K).