Thermoelectric Crystals Research Articles

From Phonons to the Thermal Properties of Complex Thermoelectric Crystals: The Case of Type-I Clathrates

From Phonons to the Thermal Properties of Complex Thermoelectric Crystals: The Case of Type-I Clathrates

Structural study of chalcogenide glasses in the Bi5As35Se60-xTex system

The atomic structure of chalcogenide glasses in the composition of As35Se60-xTexBi5 (x = 0, 5, 10, 15, 20) is investigated by XRD, Raman spectroscopy and HR-XPS. All results present the consistent evidences on association of Te addition with the structural evolution of glasses. XRD patterns show that the Te can be added into the As35Se60Bi5 system to substitute Se by maximum 15 mol% without causing crystallization. Raman and HR-XPS spectra demonstrate that the substitution of Te for Se is closely related to formation of locally ordered nanostructure in glass network. In low concentration, Te atoms are preferentially bonded with As rather than Bi, forming mixed [AsSe3-xTex] pyramid units. With the increasing of Te content, Te atoms tend to be bonded with Bi to form [BiSe3-xTex] units. In the case of Te incorporation over 20 mol%, the BiTe bond becomes further strengthened, inducing the precipitation of the sole thermoelectric crystals (Bi2Se3-xTex).

Short-range order in defective half-Heusler thermoelectric crystals

The discovery of short-range order, associated with diffuse bands in electron diffraction patterns, provides new insights into defective half-Heusler thermoelectric crystals.

High Thermoelectric Performance of p-Type Bi<sub>0.5</sub>Sb<sub>1.5</sub>Te<sub>3</sub>+<i>x</i>Te Crystals Prepared via Gradient Freezing

p-type Bi0.5Sb1.5Te3+xTe thermoelectric crystals with various percentages of Te (x = 0.00 wt.%–3.00 wt.%) excess were prepared by the gradient freeze method. By doping with different Te contents, anti-site defects, Te vacancies and hole carrier concentrations were controlled. The Seebeck coefficient, resistivity, thermal conductivity, carrier concentration, and mobility were measured. The relationships between the Te content and thermoelectric properties were investigated in detail. The results suggested that the thermoelectric figure of merit ZT of the Bi0.5Sb1.5Te3+0.09wt.% crystals was 1.36 near room temperature, the optimum carrier concentration was 1.25 × 1019 cm-3, and the mobility was 1480 cm2 V-1 S-1, respectively.

Thermoelectric crystals Bi 2Te 2.88Se 0.12 undoped and doped by CdCl 2 or CdBr 2 impurities, fabricated and characterized by XRD and Hall effect

Empirical studies on the fabrication of thermoelectric element Bi 2Te 2.88Se 0.12 undoped and doped by 0.08 wt.% CdCl 2 or CdBr 2 have been carried out. Zone melting method was employed to crystallize the solid solutions of the compounds. Structural characteristics of the grown crystals were examined by XRD technique. Measurements of thermoelectric parameters, such as electrical conductivity and Seebeck coefficient, showed a continuous deviation of the composition along the crystal growth direction. Effects of an impurity as a dopant on thermoelectric parameters were studied. Finally, Hall effect system was used to measure free carrier concentration and their mobility at 300 K. Results showed a significant increment on α 2 σ, due to dopant addition.