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Effect of crystal defects on the electronic structure and dielectric functions of In0.5Tl0.5I solid state solutions

Andriyevsky Bohdan, Kashuba A., Ilchuk H.

Zeszyty Naukowe Wydziału Elektroniki i Informatyki Politechniki Koszalińskiej

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2019

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Nr 15

35--56

EN

We investigate an influence of the various crystal structure imperfections on the electronic properties and dielectric functions for In0.5Tl0.5I semiconductor in the frame of the density functional theory calculations. The tensor of electron effective mass m*ij of InI, In0.5Tl0.5I and TlI crystals has been calculated for the valence and conduction bands and different K-points of Brillouin zone. Dielectric functions ε(hν) of the defective crystals based on In0.5Tl0.5I solid state solution with iodine vacancy and thallium interstitial atom were calculated taking into consideration the inter-band and intra-band electron transitions. The studies of the defective crystals reveal increased low-frequency and stationary electron conductivity with anisotropy resulted from the anisotropy of the electron effective mass tensor. Our findings explain the origin of crucial changes in the band structure by formation the donor half-occupied levels close to the unoccupied conduction bands due to the crystal structure defects, i.e. iodine vacancy or thallium interstitial atom. It has been shown that in the case of real crystals, in particular metal-halides, the proper consideration of defects in quantum-chemical calculations results in a better matching of the theoretical and experimental results in comparison to the case when the perfect crystal structure had been used for calculations.

PL

Zbadano wpływ różnych niedoskonałości struktury krystalicznej na właściwości elektronowe i funkcje dielektryczne półprzewodnika In0.5Tl0.5I w ramach teorii funkcjonału gęstości. Został obliczony tensor efektywnej masy elektronów m* kryształów InI, In0.5Tl0.5I i TlI dla pasm walencyjnych i przewodnictwa oraz różnych K-punktów strefy Brillouina. Funkcje dielektryczne ε(hν) domieszkowanych kryształów roztworów stałych In0.5Tl0.5I z wakansami jodu i atomami międzywęzłowymi talu zostały obliczone z uwzględnieniem międzypasmowych i wewnątrz-pasmowych przejść elektronowych. Badania domieszkowanych kryształów ujawniły zwiększoną przewodność elektronową niskoczęstotliwościową i stacjonarną o anizotropii wynikającej z anizotropii tensora efektywnej masy elektronów. Przeprowadzone badania wyjaśniają obserwowane duże zmiany struktury pasmowej pochodzące z utworzenia pół wypełnionych poziomów donorowych w pobliżu niezajętych pasm przewodnictwa wynikających z defektów struktury krystalicznej, tj. wakansów jodu czy atomów międzywęzłową talu. Wykazano, że w przypadku kryształów rzeczywistych, w szczególności halogenków metali, właściwe uwzględnienie defektów w obliczeniach kwantowo-chemicznych daje możliwość lepszego dopasowania obliczeń teoretycznych do wyników doświadczalnych w porównaniu do obliczeń bazujących na strukturze krystalicznej doskonałej.

2

Electrical transport and magnetoresistance of double layered CMR manganites R1.2Sr1.8Mn2O7(R = La, Pr, Sm)

Reddy Y. S.

Materials Science Poland

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2017

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Vol. 35, No. 2

440--446

EN

Polycrystalline bulk samples of double layered (DL) colossal magnetoresistive (CMR) manganites R1.2Sr1.8Mn2O7 (R = La, Pr, Sm) were prepared by sol-gel method to study the effect of size of lanthanide ion on their magnetotransport properties. The electrical resistivity of the samples was investigated in the temperature range of 70 K to 300 K at different magnetic fields. The samples LSMO and PSMO show insulator-to-metal transition (IMT) behavior, while SSMO sample exhibits insulating behavior in the entire temperature range with a very large value of resistivity. The insulator-to-metal transition temperature (TIM) decreases from 123 K (LSMO) to 90 K (PSMO) and disappears in SSMO sample. To explain the electrical transport above TIM, the temperature dependent resistivity data (T > TIM) of all the samples were fitted to the equations of different conduction models. The results indicate that the conduction at T > TIM is due to Mott variable range hopping (VRH) mechanism in the LSMO and PSMO samples, while Efros-Shkloskii (ES) type of VRH model dominates the conduction process in the SSMO sample. All the three samples show increasing magnetoresistance (MR) even below TIM and the maximum MR is shown by LSMO (39 % at 75 K, 3 T).

3

Test bench for battery energy storage selection for use on solar powered motor yachts

Koniak M., Czerepicki A., Tomczuk P.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2016

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nr 46 (118)

197--202

EN

An increasing number of transport vehicles, including vessels, are powered by electric engines supplied by batteries. Warsaw University of Technology, together with the Maritime University of Szczecin and industrial partners, is involved in the “Innovative yacht with hybrid drive, fueled by renewable energy sources” project, focused on the construction of a yacht driven from such a source. The biggest challenge in this field of technology is represented by the batteries. Proper assortment and exploitation can significantly extend their life cycle. For this reason, the interest in forecasting battery life cycle in specific applications has increased. In this article the authors review the types of batteries used in transport and present the design and realization of a laboratory workstation developed to test battery parameters in the context of the project. The process of gathering parameters and the testing conditions are also presented. An original IT system manages the progress of the experiments. Logged cell operating parameters will be presented along with the real, measured data.