Кафедра "Фізика"

Постійне посилання колекціїhttps://repository.kpi.kharkov.ua/handle/KhPI-Press/7578

Офіційний сайт кафедри http://web.kpi.kharkov.ua/tef

Кафедра "Фізика" створена у 2016 році шляхом об'єднання кафедри "Загальна та експериментальна фізика" і кафедри "Теоретична та експериментальна фізика", заснованої в 1972 році. .

У 1885 р. для викладання в інституті курсу фізики на посаду ад’юнкт-професора був запрошений магістр фізики приват-доцент Харківського університету Олександр Костянтинович Погорілко. У різні роки на кафедрі працювали видатні вчені-фізики: Пільчиков Н. Д., Латишев Г. Д., Обреїмов І. В., Пінес Б. Я., Ландау Л. Д., Корсунський М. І., Веркин Б. І., Дмитренко І. М., Базакуца В. А., Кулик І. О., Янсон І. К., Басс Ф. Г. Гуревич Ю. Г., Косевич В. М., Кукушкін Л. С. та ін.

Кафедра входить до складу Навчально-наукового інституту комп'ютерного моделювання, прикладної фізики та математики Національного технічного університету "Харківський політехнічний інститут".

У складі науково-педагогічного колективу кафедри працюють: 2 доктора та 16 кандидатів фізико-математичних наук, 2 кандидата технічних наук, 1 кандидат педагогічних наук; 2 співробітника мають звання професора, 12 – доцента.

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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.
Temperature and magnetic field dependences of thermoelectric properties of Bi1-xSbx solid solutions in the range x = 0-0.25
(Elsevier Ltd, 2021) Rogacheva, E. I.; Doroshenko, A. N.; Nashchekina, O. N.
Bi1–xSbx solid solutions are the best n-type thermoelectric materials for use at temperatures ≤200 K. An important parameter determining material’s figure of merit is charge carrier concentration. To determine it correctly, one should carry out measurements in a weak magnetic field. On the basis of the magnetic field dependences of the Hall coefficient and magnetoresistance, the dependences of the weak magnetic field boundary Bc on composition (x = 0–0.25) and temperature (T = 77–300 K) for polycrystalline Bi1–xSbx alloys were plotted. It was established that the Bc(x) dependences exhibit a non-monotonic behavior which is attributed to the existence of electronic phase transitions.
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.
Magnetoresistance of Polycrystalline Bi₁₋ₓSbₓ Alloys (x = 0 – 0.07)
(IEEE, 2017) Doroshenko, A. N.; Martynova, K. V.; Rogacheva, E. I.
A detailed investigation of the composition dependences of magnetoresistance for polycrystalline Bi₁₋ₓSbₓ solid solutions in a concentration range x = 0 – 0.07 was performed at 300 K in weak and strong magnetic field. It was shown that the composition dependences of magnetoresistance are clearly expressed nonmonotonic type. The presence of concentration anomalies of magnetoresistance was confirmed that had been earlier observed in the range x = 0 – 0.1 on cast samples after different kinds of thermal treatment and interpreted as a manifestation of electron phase transitions. It is shown that the position of the extrema does not depend on the magnitude of the magnetic field in the interval 0.01 - 1.0 T.
Thermoelectric properties of polycrystalline Bi₁₋ₓSbₓ solid solutions in the concentration range x = 0 – 0.25
(National Academy of Sciences of Ukraine, 2016) Doroshenko, A. N.; Rogacheva, E. I.; Drozdova, A. A.; Martynova, K. V.; Men'shov, Yu. V.
A detailed investigation of the dependence of thermoelectric properties of polycrystalline Bi₁₋ₓSbₓ solid solutions on composition in a wide concentration range (x = 0 – 0.25) was performed at room temperature. The objects of study were cast samples of various composition obtained by ampoule method in one technological cycle consisting in cooling of ampoules with melts in the air and subsequent long homogenizing annealing at temperature (520 ± 5) K for 720 hours. It was shown that the composition dependences of properties are of clearly expressed nonmonotonic type. The presence of concentration anomalies of thermoelectric properties was confirmed that had been earlier observed in the range x = 0 – 0.1 on cast samples after different kinds of thermal treatment and interpreted as manifestation of electron phase transitions. A complicated nature of dependences at x > 0.1 is attributable to qualitative changes in Bi₁₋ₓSbₓ band structure at certain critical compositions, a change in relative contribution to conductivity of charge carriers from different energy bands with a change in antimony concentration and high sensitivity of energy spectrum and physical properties of Bi₁₋ₓSbₓ к to external effects.
Galvanomagnetic properties of polycrystalline Bi₁₋ₓSbₓ solid solutions in the concentration range x = 0-0.25
(Науково-технологічний комплекс "Інститут монокристалів", 2020) Rogacheva, E. I.; Doroshenko, A. N.; Drozdova, A. A.; Nashchekina, O. N.; Men'shov, Yu. V.
The dependences of the Hall coefficient, electrical conductivity, magnetoresistance, electron and hole concentration and mobility on the Bi₁₋ₓSbₓ solid solution composition in the concentration range x = 0-0.25 at 77 and 300 K in magnetic fields 1 T and 0.05 T were obtained. It was shown that all the dependences exhibit a distinct nonmonotonic oscillating behavior at both temperatures and in both magnetic fields. The presence of concentration-dependent anomalies of galvanomagnetic properties is attributed to critical phenomena accompanying the percolation-type transition from dilute to concentrated solid solutions and electronic phase transitions: a transition to a gapless state, the semimetal – semiconductor transition, and indirect – direct band gap semiconductor transition.
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.
Temperature and concentration dependences of specific heat of Bi₁₋ₓSbₓ solid solutions
(Науково-технологічний комплекс "Інститут монокристалів", 2018) Rogacheva, E. I.; Doroshenko, A. N.; Nashchekina, O. N.
For Bi₁₋ₓSbₓ solid solutions, the concentration (x = 0 - 0.12) and temperature (170-525 K) dependences of specific heat Cp were obtained. At all temperatures studied, three peaks of Cp were observed near x = 0.015, x = 0.037, and x = 0.07. The observed effects were attributed to critical phenomena accompanying the second-order phase transitions: percolation transition from dilute to concentrated solid solutions, the transition to a gapless state, and the semimetal-semiconductor transition, respectively. It was shown that the values of critical indexes (α = 0.11 ± 0.01) are the same not only for different peaks but also for different temperatures and correspond to the values theoretically calculated within the framework of scale-invariant theory for three-dimensional (3D) models.

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