J. Navrátil

Defect structure of Pb-doped Bi2Te3 single crystals

Pb-doped Bi2Te3 single crystals with a Pb concentration of c Pb = 0−9.4 ×  1025 m−3 were prepared from the elements Bi, Pb and Te of 99.999% purity by means of the Bridgman method. Samples of these crystals were characterized by measurements of the Hall coefficient R H(B∥c), electrical conductivity σ⊥c and Seebeck coefficient α(c⊥ΔT) over the temperature range 90–420 K. It was found that Pb impurities in Bi2Te3 behave as acceptors; some (40%) of the incorporated Pb atoms are electrically inactive. This effect is explained by the model of crystal lattice defects based on the assumption that the Pb atoms interact with native defects in the crystal lattice of undoped Bi2Te3, that is with antisite defects and vacancies in the Te sublattice.

Thermoelectric Properties of Cu2HgSnSe4-Cu2HgSnTe4 Solid Solution

Copper-based semiconductors from the family Cu2-II-IV-VI4 have recently attracted a great deal of attention because of their promising thermoelectric (TE) properties. Polycrystalline samples from the Cu2HgSnSexTe4−x (x = 0, 0.8, 2, 3.2, 4) solid solution were prepared and structurally characterized by powder x-ray diffraction. The samples from this solid solution crystallize in the stannite structure (space group

High-temperature thermoelectric properties of Hg-doped CuInTe2

I\bar{4}2m

Study of Yb-Doped CoSb3 Thermoelectric Thin Films Prepared by Laser

I4¯2m). Transport, TE, and thermal properties of hot-pressed samples are reported. About a 20 % reduction in calculated lattice thermal conductivities, compared to the lattice thermal conductivities of pure components of the alloys (i.e. Cu2HgSnSe4 and Cu2HgSnTe4), was observed for Cu2HgSnSe2Te2 alloy. The maximum ZT of the Cu2HgSnSe2Te2 sample reaches 0.6 at 575 K.

Thermoelectric Properties of RuSb2Te Ternary Skutterudites

The properties of thin thermoelectric layers (about 60 nm in thickness) prepared by pulsed laser deposition are presented. Hot pressed targets were made from “middle” temperature range thermoelectric bulk materials with the potential high figure of merit ZT. P-type and N-type layers were prepared from Yb0.19Co4Sb12 and Ce0.1Fe0.7Co3.3Sb12 targets, respectively. The thin films were deposited on quartz glass substrates using KrF excimer laser. The individual layers were prepared by applying different laser beam energy densities (2 or 3 J cm−2) at several substrate temperatures (200, 250, or 300 °C). Crystallinity and composition of the layers were examined by x-ray diffraction and wavelength dispersive analysis, respectively. Homogeneity of Yb across a surface of the Yb filled film was explored by secondary ion mass spectrometry. The thermoelectric properties, the Seebeck coefficient, the electrical resistivity, and the power factor, for the best prepared P and N layer are presented in the temperature range...

Some physical properties of Hf-doped Sb/sub 2/Te/sub 3/ single crystals

Polycrystalline samples of composition CuIn1−xHgxTe2 (x = 0–0.21) were synthesized from elements of 5N purity using a solid state reaction. The phase purity of the products was verified by X-ray diffraction. Samples for transport property measurements were prepared using hot-pressing. The samples were characterized by measurement of the electrical conductivity, Hall coefficient, Seebeck coefficient, and thermal conductivity over a temperature range of 300–675 K. All samples show p-type conductivity. We discuss the influence of Hg substitution on the free carrier concentration and thermoelectric performance. The investigation of the thermoelectric properties shows up to a 40% improvement of ZT in the temperature range of 300–600 K.

Conduction band splitting and transport properties of Bi2Se3.

The synthetic analogue of the mineral tischendorfite, Pd 8 Hg 3 Se 9 , was prepared using the silica glass tube technique and its crystal structure was solved and refined from powder X-ray diffraction data. The structure is orthorhombic, space group Pmmn , with a = 7.1886(2), b = 16.8083(5), c = 6.4762(2) A, V = 782.51(4) A 3 and Z = 2. There are three Pd, two Hg and four Se independent positions. Tischendorfite crystallizes in a framework structure, where Pd atoms show two types of coordination by Se atoms: [PdSe 4 ] squares and [PdSe 5 ] pyramids. The [PdSe 5 ] pyramid shares two opposite Se–Se edges with adjacent pyramids forming linear isolated chains running along the a -axis, whereas [PdSe 4 ] squares are paired via one common Se–Se edge. The paired squares and chains of pyramids form characteristic slabs parallel to (010). Both types of slabs alternate along the b -axis. The Hg atoms occupy the anti-cubooctahedral voids formed by Se atoms. The structure is stabilized by a system of Pd–Hg and Pd–Pd metallic bonds.

Behavior of Ag Admixtures in Sb2Te3and Bi2Te3Single Crystals

Thin films of Yb filled CoSb3 were prepared on fused silica substrates using pulsed laser deposition method. The stoichiometric Yb0.19Co4Sb12 target was prepared by hot pressing method. The deposition conditions were changed with the goal to reach layers of smooth morphology. The target-to substrate distance was kept equal to 4 cm. The ambient argon pressure moved from 0.5 Pa to 13 Pa, laser repetition rate from 3 Hz to 10 Hz, and substrate temperature from 250 °C to 400 °C. We tested laser fluencies from 0.8 J·cm-2 to 5 J·cm-2. Films roughness was determined by mechanical profilometer and by atomic force microscopy. The lowest roughness of about 5 nm – 10 nm was reached for low laser fluencies but mechanical quality of films was poor and growth rate low (about 0.1 A/pulse). From WDX analysis follows that there is an excess of Yb and Sb compared to Yb0.19Co4Sb12 target.