Search

Abstract: Reversible electrochemical lithium intercalation/deintercalation reactions have been applied to integrally modify the thermoelectric performance of Bi2Se0.3Te2.7 compounds. The carrier concentration of Bi2Se0.3Te2.7 has been precisely controlled experimentally through the adjustment of the residual lithium content. The variations of electronic transport properties of Li x Bi2Se0.3Te2.7, including electrical conductivity, Seebeck coefficient and carrier concentration, as a function of the intercalated lithium amount (x), show a special non-monotonic P-type to N-type doping trend. This variation is caused by the competition of two mechanisms controlling the carrier concentration: (i) decreasing of the Se/Te ratio through a Li–Se reaction that reduces the amount of the TeBi or SeBi antisite defects and therefore the electron concentration; (ii) n-type doping by lithium that provides the electron. Moreover, the nanoparticle exfoliation during lithium intercalation and deintercalation reactions leads to the formation of an internal nanocrystalline composite structure which effectively reduces the lattice thermal conductivity. Through an integral modification of both electrical and thermal transport properties, the maximum ZT value of Li x Bi2Se0.3Te2.7 was improved by nearly 25%. [Copyright &y& Elsevier]

Abstract: Two crystals of Bi2Se0.21Te2.79 doped with 0.08wt% TeI4 were grown by zone melting on the Foton-M3 spacecraft of Russia and the ground in 2007, respectively. The chemical composition, structure and thermoelectric properties of the space and ground crystals grown were evaluated by EPMA, XRD and thermoelectric measurements including Seebeck coefficient, electrical conductivity and thermal conductivity. The compositions of the space crystal grown along growth direction were more homogeneous than that of the ground crystal grown. The crystallization of space crystal grown was obviously improved. The maximum ZT value of space crystal reached 1.14 at 300K, which was higher about 29% than that of ground crystal at room temperature. These results imply that the composition homogeneity and crystallization of Bi2Se0.21Te2.79 crystal can be improved under microgravity conditions, which is helpful for enhancing thermoelectric figure of merit of Bi2Te3-base materials. [Copyright &y& Elsevier]

Lithium intercalation and de-intercalation processes have been used to fabricate bulk Bi2Se0.3Te2.7with internal nanostructures. The doped Li content can be precisely controlled through this method. It provides a chance to directly optimize electrical properties when preparing nano-structured materials, leading to the optimum carrier concentration for improved thermoelectric figure of merit. [ABSTRACT FROM AUTHOR]

The low weighted carrier mobility has long been considered to be the key challenge for improvement of thermoelectric (TE) performance in BiTeI. The Rashba-effect-induced two-dimensional density of states in this bulk semiconductor is beneficial for thermopower enhancement, which makes it a prospective compound for TE applications. In this report, we show that intercalation of minor Cu-dopants can substantially alter the equilibria of defect reactions, selectively mediate the donor-acceptor compensation, and tune the defect concentration in the carrier conductive network. Consequently, the potential fluctuations responsible for electron scattering are reduced and the carrier mobility in BiTeI can be enhanced by a factor of two to three between 10 K and 300 K. The carrier concentration can also be optimized by tuning the Te/I composition ratio, leading to higher thermopower in this Rashba system. Cu-intercalation in BiTeI gives rise to higher power factor, slightly lower lattice thermal conductivity, and consequently improved figure of merit. Compared with pristine BiTe0.98I1.02, the TE performance in Cu0.05BiTeI reveals a 150% and 20% enhancement at 300 and 520 K, respectively. These results demonstrate that defect equilibria mediated by selective doping in complex TE and energy materials could be an effective approach to carrier mobility and performance optimization. [ABSTRACT FROM AUTHOR]