A. A. Kudryashov

The Shubnikov-de Haas effect and thermoelectric properties of Tl-doped Sb2Te3 and Bi2Se3

The influence of doping with Tl on the Shubnikov-de Haas effect at T = 4.2 K in magnetic fields up to 38 T in p-Sb2−xTlxTe3 (x = 0, 0.005, 0.015, and 0.05) and n-Bi2−xTlxSe3 (x = 0, 0.01, 0.02, 0.04, and 0.06) single crystals is investigated. Extreme cross-sections of the Fermi surface in both materials decrease upon doping with Tl: the hole concentration decreases in Sb2−xTlxTe3 due to the donor effect of Tl and the electron concentration in n-Bi2−xTlxSe3 decreases due to the acceptor effect of Tl. The temperature dependences of the Seebeck coefficient, electrical conductivity, thermal conductivity, and dimensionless thermoelectric figure of merit in a temperature range of 77–300 K are measured. The thermal conductivity and electrical conductivity decrease upon doping with Tl both in p-Sb2−xTlxTe3 and in n-Bi2−xTlxSe3. The Seebeck coefficient increases in all compositions upon an increase in doping over the entire measured temperature range. The thermoelectric figure of merit increases upon doping with Tl.

Influence of Thallium on the Shubnikov - de Haas effect and Thermoelectric Properties of Sb2Te3 and Bi2Se3

Influence of Tl-doping on the Shubnikov de Haas effect (SdH) at T=4.2 K in magnetic field up to 38 T of p-Sb2-xTlxTe3 (x=0; 0.005; 0.015; 0.05) and n-Bi2-xTlxSe3 (x=0, 0.01; 0.02; 0.04; 0.06) single crystals has been investigated. By increasing the Tl content, the frequency of the SdH effect and hence the extremal cross-sections of the Fermi-surface decreases in both materials. The hole concentration decreases in Sb2-xTlxTe3 due to a donor effect of Tl and the electron concentration decreases in n-Bi2-xTlxSe3 due to an acceptor effect of Tl. Temperature dependence of the Seebeck coefficient S, electrical conductivity σ, thermal conductivity k and the figure of merit ZT single crystals were measured in the temperature range 77 K - 300 K. The values of k and σ decrease due to Tl doping in Sb2-xTlxTe3 and n-Bi2-xTlxSe3 and the Seebeck coefficient S for all compositions increases in the whole temperature range. The figure of merit ZT increases in both materials. The preferential scattering mechanism in Tl-doped samples changes from the acoustic phonon scattering to the ionized impurity scattering.

Thermoelectric properties of BiTeBr and BiTeI single crystals and composites of BiTeI with BiI3, CuI and Bi

Thermoelectrical properties of BiTeI and BiTeBr single crystals are investigated. For both crystals, the band structure is calculated from the density-functional theory. It is shown that both compounds are semiconductors. Temperature dependence of conductivity, Seebeck coefficient and thermal conductivity are measured in the temperature interval 5<T<300 K. Both semiconductors have n-type conductivity. The figure of merit for BiTeBr is much higher than that of BiTeI, which is related mainly to a larger Seebeck coefficient for the former compound. Influence of BiI3, CuI and superstohiometric Bi on there galvanomagnetic and thermoelectric properties of BiTeI are investigated. Seebeck coefficient of composite of BiTeI with CuI essentially increases while thermoconductivity decreases. The same is observed for samples with BiI3. Superstohiometric Bi decreases thermoconductivity and electroconductivity and has almost no influence on thermopower.

Thermoelectric properties, Shubnikov–de Haas effect and mobility of charge carriers in bismuth antimony tellurides and selenides and nanocomposite based on these materials

We describe here the study of the Shubnikov–de Haas effect and thermoelectric properties of p-(Bi0.5Sb0.5)2Te3 single crystals doped with Ga, n-Bi2–xTlxSe3 and p-Sb2–xTlxTe3. Using Fourier spectra of the oscillations we calculated the mobility of charge carriers and its variation upon doping. We found that Ga has a donor effect in p-(Bi0.5Sb0.5)2Te3, Tl is an acceptor in n-Bi2–xTlxSe3 and increases the mobility of electrons, while in p-Sb2–xTlxTe3, Tl is a donor and decreases the mobility of holes. We consider the evolution of the defectiveness of crystals that leads to the observed effects. We also synthesized and investigated nanocomposites of solid solutions Sb2Te3–xSex (0 < x < 1). When Se concentration increases in Sb2Te3–xSex, the concentration of holes decreases. At the same time the Seebeck coefficient decreases. This is not typical for semiconductors but correlates with the earlier data. A theoretical model was developed to calculate simultaneously the dependences of the Seebeck coefficient, Hall...

Effect of thallium doping on the mobility of electrons in Bi2Se3 and holes in Sb2Te3

The Shubnikov–de Haas effect and the Hall effect in n-Bi2–xTlxSe3 (x = 0, 0.01, 0.02, 0.04) and p-Sb2–xTlxTe3 (x = 0, 0.005, 0.015, 0.05) single crystals are studied. The carrier mobilities and their changes upon Tl doping are calculated by the Fourier spectra of oscillations. It is found shown that Tl doping decreases the electron concentration in n-Bi2–xTlxSe3 and increases the electron mobility. In p-Sb2–xTlxTe3, both the hole concentration and mobility decrease upon Tl doping. The change in the crystal defect concentration, which leads to these effects, is discussed.

Influence of Magnetic Impurities on Thermoelectric Capabilities of Bi2Te3, Sb2Te3, and Bi2Se3

Temperature dependencies of the Seebeck coefficient, electrical conductivity, heat conductivity and the dimensionless thermoelectric figure of merit ZT of p-Bi2Te3, n-Bi2Se3 and Sb2Te3 doped by Fe or Cr have been investigated in the temperature interval 7 < T < 300 K. At T=4.2 K the Shubnikov-de Haas and Hall effects have been measured. By increasing the Fe content, the hole concentration decreases in p-Bi2-xFexTe3, while the electron concentration increases in n-Bi2-xFexSe3. The hole concentration decreases in Sb2-xCrxTe3 with Cr doping. This demonstrates that Fe or Cr act as donors. The Seebeck coefficient increases in p-Bi2-xFexTe3 and Sb2-xCrxTe3 with increasing Fe or Cr content, while it decreases in n-Bi2-xFexSe3.

Thermoelectric properties of Bi{sub 2}Te{sub 3}, Sb{sub 2}Te{sub 3} and Bi{sub 2}Se{sub 3} single crystals with magnetic impurities

Temparature dependence of Seebeck coefficients S, electrical conductivity, heat conductivity k and dimensionless thermoelectric figure of merit ZT of p-Bi{sub 2}Te{sub 3}, Sb{sub 2}Te{sub 3} and n-Bi{sub 2}Se{sub 3}-doped by Fe or Cr were carried out in the temperature interval 7150 K. - Graphical abstract: Temparature dependence of Seebeck coefficients S, electrical conductivity {sigma}, heat conductivity k and dimensionless thermoelectric figure of merit ZT of p-Bi{sub 2}Te{sub 3}, Sb{sub 2}Te{sub 3} and n-Bi{sub 2}Se{sub 3} doped by Fe or Cr were measured in the temperature interval 7150 K up to ZT=0.4 as shown in figure. Highlights: Black-Right-Pointing-Pointer Fe and Cr act as donors in Bi{sub 2}Te{sub 3}, Sb{sub 2}Te{sub 3} and Bi{sub 2}Se{sub 3.} Black-Right-Pointing-Pointer The Seebeck coefficient increases in p-Bi{sub 2-x}Fe{sub x}Te{sub 3} and Sb{sub 2-x}Cr{sub x}Te{sub 3}. Black-Right-Pointing-Pointer Dimensionless figure of merit ZT increased up to 0.4 in Cr-doped Sb{sub 2}Te{sub 3} at T=300 K.

Thermoelectric Properties of Bi2Te3, Sb2Te3and Bi2Se3Single Crystals with Magnetic Impurities.

The thermoelectric properties of single crystals of Fe- or Cr-doped p-Bi2Te3, Sb2Te3, and n-Bi2Se3 are characterized by Seebeck coefficient, electrical conductivity, and heat conductivity measurements between 7 and 300 K.