Thermoelectric power of GeTe-rich (GeTe)1–x(AgBiTe2)x solid solutions

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The thermoelectric power S of GeTe‐rich (GeTe)1‐x(Bi2Te3)x solid solutions (0 ≦ x ≦ 0.05) is investigated as a function of composition x and temperature T in the range from 80 to 350 K, where the materials have the crystal and band structure of the rhombohedral α‐phase of GeTe. On the basis of the non‐parabolic two‐band Kane model of IV‐VI compounds information on the Fermi energy F (reduced Fermi energy F* = F/k0T, where k0 is the Boltzmann constant) and the degeneracy of the alloys is deduced. A qualitative interpretation of the temperature and composition dependences of S is made. It is assumed that there are two types of carriers (light and heavy holes) and redistribution among the valence bands with the change of temperature.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermoelectric Power of (GeTe)1−x(Bi2Te3)x Solid Solutions (0 ≦x ≦ 0.05) in the Temperature Interval 80 to 350 K

Christakudi¹,

Plachkova²,

Christakudis³

1995

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“…This determines the transport coefficient changes for the SS. 6, 8, and 10) are measured and discussed before [7] dependence of S of GeTe) of width of about 100 to 200K, which is shifted to higher temperatures with increasing AgBiTe, content in the alloys. The reason for this may be some decrease of the Debye temperature for solid solutions by substituting Ge atoms (atomic weight 72.5) in the cation sublattice by heavy Ag (atomic weight 107.868) and Bi (atomic weight 208.980) atoms.…”

Section: The Band Structures Of Rhombohedral Gete and Ss On Its Basementioning

confidence: 99%

Thermoelectric Power of Some Compositions of GeTe-Rich (GeTe)1—x(AgBiTe2)2 Solid Solution

Plachkova

Georgiev

1993

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A method of preparation of single phase ingots of GeTe-rich solid solutions (x s 0.20) in the system (GeTe), _JAgBiTe,), is developed. The temperature dependence (77 to z 900 K) of thermoelectric power is measured. The curves for GeTe and GeTe-rich solid solutions are of similar shape. Using the conventional transport theory the lattice and electronic contributions to this effect are obtained. To explain the behavior of diffusion and phonon drag terms the metallic expressions for both are used. On the basis of band-edge models of GeTe and AgBiTe, and the nonparabolic two-band Kane model of IV-VI compounds and separate values of the electronic parts of the thermoelectric power an information about the Fermi energy and the degree of degeneracy is received. A qualitative interpretation of the temperature dependence of S , is made.

X-ray study of defects in the GeTeAg2TeBi2Te3 system

Plachkova

Georgieva²,

Petrov

et al. 1989

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The lattice parameters (a, αR), the change and formation of defects in (GeTe)1−x[(Ag2Te)1−y · (Bi2Te3)y]x solid solutions (SS) vs. the amount of introduced Ag and Bi atoms, and vacancies in cation sublattice at 300 K are studied. X‐ray powder patterns results and also pycnometric density measurements are used. The SS structure changes from rhombohedral to cubic with increasing the number of introduced Ag and Bi atoms, are determined by the parameter \documentclass{article}\pagestyle{empty}\begin{document}$ Z = \frac{{x\left({1 + 2y} \right)}}{{1 + 2xy}} $\end{document}. At equal Z the structure is near to cubic at the greatest amount of Bi atoms (greatest y). The deviation from stoichiometry arising from the SS formula leads to the formation of additional vacancies (+ VN) at y > 0.5 or “excess” cations (− VN) at y < 0.5, the amount of which changes linearly with composition (Z).