Tuning the Saturated Vapor Pressure of Solvothermal Synthesis to Boost the Thermoelectric Performance of Pristine Bi2Te3 Polycrystals by Anisotropy Strengthening

Bi2Te3 is one of the most promisingthermoelectricmaterials that target near-room-temperature applications due to itshigh thermoelectric potential at these temperatures. In this work,we report a new route to significantly improve the thermoelectricperformance of pristine Bi2Te3 polycrystals.We design the mixed solutions composed of H2O and ethyleneglycol (EG) as novel solvents to solvothermally synthesize Bi2Te3 crystalline microplates. It is found that theaddition of H2O can boost the saturated vapor pressureof the mixed solutions during the solvothermal synthesis and significantlydrive the crystal growth of Bi2Te3 microplatesalong their in-plane directions due to the tuning of kinetic conditions.Such a unique route strengthens the anisotropy of the bulk materialssintered from these microplates, leading to improved carrier mobilityof >170 cm(2) V-1 s(-1) and in turn a high electrical conductivity of >1400 S cm(-1) at room temperature. Combined with a high absoluteSeebeck coefficientof >140 mu V K-1, a competitively high powerfactor of similar to 30 mu W cm(-1) K-2 can be achieved in the solvothermally synthesized samples. Besides,compared with the bulk material sintered from commercial Bi2Te3 powders with a figure of merit of 0.2 at 369 K, thefigure of merit of the bulk material developed in this work is significantlyimproved by similar to 167% (0.56), indicating great potential for practicalapplications. This work paves a new way and fills the gap of boostingthe thermoelectric performance of pristine Bi2Te3.

Automated summary

In this work, a new method was reported to significantly improve the thermoelectric performance of pristine Bi2Te3 polycrystals by solvothermally synthesizing Bi2Te3 crystalline microplates using mixed solutions composed of H2O and ethylene glycol (EG) as solvents. The addition of H2O increased the saturated vapor pressure of the mixed solutions and promoted the crystal growth of Bi2Te3 microplates along their in-plane directions, resulting in strengthened anisotropy of the sintered bulk materials and improved carrier mobility and electrical conductivity at room temperature. The figure of merit of the developed bulk material was significantly improved by about 167% compared to the bulk material sintered from commercial Bi2Te3 powders, indicating great potential for practical applications. This work paves a new way and fills the gap of boosting the thermoelectric performance of pristine Bi2Te3.