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Публікація Percolation effects and self-organization processes in cold-pressed Bi2(Te1−xSex)3 solid solutions(Elsevier Ltd, 2021) Rogacheva, E. I.; Martynova, E. V.; Shelest, T. N.; Doroshenko, A. N.; Nashchekina, O. N.It was established that the dependences of thermoelectric and mechanical properties of cold-pressed Bi2(Te1−xSex)3 alloys on composition (x = 0–0.07) exhibit a non-monotonic behavior in certain concentration ranges: an anomalous decrease in the Seebeck coefficient, thermoelectric power factor, and microhardness, and increase in electrical conductivity with increasing x. We observed similar anomalies earlier for cast Bi2(Te1−xSex)3 alloys and explained them by percolation and self-organization phenomena. Thus, the existence of the anomalies does not depend on the method of sample preparation. However, in pressed samples as compared to cast ones conductivity type changes from p to n and thermoelectric power factor increases.Публікація Percolation effects and self-organization processes in Bi₂(Te₁₋ₓSeₓ)₃ solid solutions(Easy Conferences Ltd, 2019) Rogacheva, E. I.; Shelest, T. N.; Martynova, E. V.; Doroshenko, A. N.; Nashchekina, O. N.Публікація Peculiarities of concentration dependences of thermal conductivity in (PbTe)₁₋ₓ (Bi₂Te₃)ₓ semiconductor solid solutions(Інститут термоелектрики НАН України, 2014) Rogacheva, E. I.; Vodorez, O. S.; Nashchekina, O. N.; Dresselhaus, M. S.For the semiconductor (PbTe)₁₋ₓ (Bi₂Te₃)ₓ solid solutions, the temperature (T = 250 – 670 K) and concentration (x = 0 – 0.07) dependences of the total λ and lattice λp thermal conductivities were obtained. It was established that the dependences λ(x), λp(x) and β(x) (where β is the exponent in the λp ~ T⁻ᵝ dependence) have a non-monotonic dependence on x in this range of x. While showing a general tendency to decrease with increasing x, the three variables λ, λp, and β exhibit maxima at x = 0.005, 0.015 and x = 0.03. The oscillatory character of these dependences is attributable to the changes in thermal transfer processes and the mechanisms of phonon scattering under transitions from the dilute to the concentrated and associated solid solutions, with the transitions due to spatial ordering processes. The effective cross-section σs for phonon scattering by impurity atoms was estimated on the basis of the experimental data and theoretical calculations in accordance with the Klemens theory. The mean σs value in the homogeneity region of PbTe (x = 0 – 0.05) found experimentally coincides with the theoretically calculated σs value. However, in the region of the dilute solid solutions (x < 0.005), the σs value considerably exceeds the mean σs value. Also long-term aging reduces λ by ~ 15%.Публікація Percolation effects and self-organization processes in Bi₂(Te₁₋ₓSeₓ)₃ solid solutions(Науково-технологічний комплекс "Інститут монокристалів", 2019) Rogacheva, E. I.; Shelest, T. N.; Martynova, E. V.; Doroshenko, A. N.; Nashchekina, O. N.; Men'shov, Yu. V.The room-temperature dependences of microhardness H, electrical conductivity σ, the Seebeck coefficient S, and thermoelectric power factor P on composition of Bi₂(Te₁₋ₓSeₓ)₃ solid solutions were measured in the concentration range x = 0 - 0.07. In the intervals x = 0.0075 - 0.0175 and x = 0.025 - 0.035, an anomalous decrease in H and S and increase in σ with increasing x were observed. The first concentration-dependent anomaly was attributed to critical phenomena, accompanying a percolation-type phase transition. The percolation threshold xc and the radius of deformation spheres R₀ around Se impurity atoms were estimated. The second anomaly is assumed to be connected with a short-range ordering in the solid solution. The non-monotonic character of the dependences of H on the load on an indenter, whose behavior depended on the impurity concentration, was attributed to the interaction of the deformation fields created by dislocations and impurity atoms.