The six independent elastic constants of the monocrystalline, pseudo-binary alloy Bi1·60Sb0·40Te3 have been measured by the ultrasonic pulse-echo technique. The elastic behaviour is compared and contrasted with those of Bi2Te3 and the group V semimetals with crystal structures belonging to the same point group, ¯3m. Elastic wave-velocity surface cross-sections, particle displacement and energy flux vectors are presented and discussed; the pure mode axes — knowledge of which is most useful in experimental ultrasonic studies — are given. Elastic wave propagation in Bi1.60Sb0.40Te3 and Bi2Te3 shows characteristics expected for layer-type crystals with weak interlayer binding, i.e., comparatively large ultrasonic velocities in thexy plane and lower velocities along the direction (z) of weakest binding.

Elastic wave propagation in Bi1⋅60Sb0⋅40Te3 and Bi2Te3

Thermoelectric properties of p-type Pb-doped Bi85Sb15−xPbx alloys at cryogenic temperatures

Low-temperature thermoelectric properties of Bi85Sb15−xNbx alloys prepared by high-press sintering

Bi85Sb15−x Pb
 x
 (x = 0, 0.5, 1, 2, 3) alloys have been prepared by the mechanical alloying–spark plasma sintering (MA-SPS) method. X-ray diffraction and scanning electron microscopy were used to characterize the microstructure of the alloys. The effect of Pb content on the thermoelectric properties was investigated in the temperature range 77–300 K. The results showed that the electrical transport properties of the Bi–Sb alloys changed from n-type to p-type with substitution of Sb by Pb. The maximum power factor reached 1.6 × 10−3 W/mK2 at 190 K, a significant improvement on values reported elsewhere. This study demonstrated that high-performance p-type thermoelectric Bi–Sb materials can be obtained by spark plasma sintering.

Improved Thermoelectric Properties of p-Type Bismuth Antimony-Based Alloys Prepared by Spark Plasma Sintering

BiSb nanoparticles were synthesized by solvothermal method. The synthesized material having a trigonal structure with space group R3m was confirmed through X-ray diffraction pattern. The Williamson-Hall method was employed to analyze the lattice stress and micro-strain produced in the BiSb nanoparticles. On the prepared material surface morphology studies were carried out using HR-SEM with EDXA. UV-visible absorption spectrum shows a wide absorption peak at 287 nm and the estimated band gap value is at Eg = 1.6 eV (from Tauc plot). The values of remanent polarization Pr = 0.156 μC/cm2, saturation polarization Ps = 0.253 μC/cm2, and coercive electric field Ec = 13.5 kV/cm obtained from the loop were close to the value. The BiSb nanoparticles exhibit semi-metallic-reported characteristics. This material is useful for thermoelectric power generation applications.

A Facile Synthesis Method of BiSb Nanoparticles for Thermoelectric Applications

The Seebeck coefficient, thermal conductivity and electrical conductivity of crystals of Bi95Sb5 doped with various amounts of Te have been measured at 80 K, using samples that were oriented so as to yield the highest thermoelectric figure of merit. A dimensionless figure of merit of 058 has been observed for a crystal doped with nominally 0002 at.% Te in a magnetic field of 04 T, this being significantly higher than the best value that was found for an intrinsic crystal. From the change of thermal conductivity with magnetic field it has been possible to estimate a value of 2.8 W m−1 K−1 for the lattice conductivity. A rather low Lorenz number is attributed to inelastic scattering of the electrons.

H J Goldsmid

Papers

The magneto-Peltier-Seebeck figure of merit of Te-doped Bi95Sb5 at 80 K