Вісники та науково-технічні збірники, журнали
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Item Дослідження кінетичних характеристик чутливих елементів термоперетворювачів на основі Ti1-xMoxCoSb(Видавництво Львівської політехніки, 2019-02-28) Крайовський, В. Я.; Рокоманюк, М. В.; Ромака, В. А.; Ромака, Л. П.; Стадник, Ю. В.; Горинь, А. М.; Krayovskyy, Volodymyr; Rokomanyuk, Mariya; Romaka, Volodymyr; Romaka, Lyubov; Stadnyk, Yuriy; Horyn, Andriy; Національний університет “Львівська політехніка”; Львівський національний університет ім. І. Франка; Lviv Polytechnic National University; Ivan Franko National University of LvivВиконано математичне моделювання та експериментальні вимірювання кінетичних та енергетичних характеристик чутливих елементів термоперетворювачів на основі термометричного матеріалу Ti1-xMoxCoSb у діапазоні температур 80–400 К. Попередні дослідження електрофізичних, енергетичних та структурних властивостей термометричних матеріалів, отриманих легуванням напівгейслерової фази TiCoSb атомами Ni та V, відповідно, показали, що вони володіють стабільними та відтворюваними характеристиками у температурному діапазоні 4,2–1000 К. Встановлено, що результати моделювання термометричних характеристик чутливих елементів на основі TiCo1-xNixSb та Ti1-xVxCoSb не узгоджувалися з результатами експериментальних вимірювань, що унеможливило їхнє використання для виготовлення чутливих елементів термометрів опору та термоелектричних перетворювачів. Моделювання електронної структури термометричних матеріалів Ti1-xMoxCoSb методом функцій Гріна (метод Корінги–Кона–Ростокера (KKR)) у наближенні когерентного потенціалу (Coherent Potential Approximation) та локальної густини (Local Density Approximation) з використанням ліцензованого програмного забезпечення AkaiKKR та SPR-KKR для обмінно- кореляційного потенціалу з параметризацією Moruzzi-Janak-Williams показало, що заміщення атомів Ti на Mo генерує у кристалі структурні дефекти донорної природи (у Mo більше 3d-електронів, ніж у Ti), а в забороненій зоні поблизу зони провідності εС утворюється домішковий донорний рівень (зона) 2D e. Експериментальні вимірювання електрокінетичних характеристик термометричних матеріалів Ti1-xMoxCoSb встановили наявність високотемпературних активаційних ділянок на залежностях питомого опору ln(ρ(1/T)), що вказує на розташування рівня Фермі εF у забороненій зоні напівпровідника, а це можливо за умови генерування акцепторів, які захоплюють вільні електрони, зменшуючи їхню концентрацію, та гальмують рух рівня Фермі εF до рівня протікання зони провідності εС. Отже, легування сполуки TiCoSb домішкою Mo призводить до генерування у кристалі структурних дефектів акцепторної та донорної природи. Встановлено механізми електропровідності чутливих елементів термоперетворювачів.Item Дослідження термометричного матеріалу HF1-хErxNiSn(Видавництво Львівської політехніки, 2016) Крайовський, Володимир; Національний університет “Львівська політехніка”Досліджено енергетичні, кінетичні та магнітні характеристики термометричного матеріалу Hf1-xErxNiSn у діапазонах T = 80÷400 K, x=0÷0.10 за напруженості магнітного поля H £10 кГс. Показано, що характеристики Hf1-xErxNiSn чутливі до зміни температури і він може бути основою для виготовлення чутливих елементів термоперетворювачів. Исследованы энергетические, кинетические и магнитные характеристики термометрического материала Hf1-xErxNiSn в диапазонах: T = 80÷400 K, x=0÷0.10 при напряженности магнитного поля H £ 10 кГс. Показано, что характеристики Hf1-xErxNiSn чувствительны к изменениям температуры и он может быть основой для изготовления чувствительных элементов термопреобразователей. The electron energy state, magnetic and transport characteristics of of thermometric materials Hf1-xErxNiSn were investigated in the T = 80÷400 K temperature range and at charge carriers concentration from x=01÷0.10 and H £ 10 kGs. The material Hf1-xErxNiSn is sensitive to the temperature change and could be used as the basis for the sensitive thermoelectric devices. We investigated the crystal structure, electron density of states (DOS) and the kinetic and energy characteristics of n-HfNiSn heavily doped with the Er impurity. Samples were synthesized at the laboratory of the Institute of Physical Chemistry, Vienna University. The Hf1-xErxNiSn crystal-lattice periods were determined by X-ray analysis with the use of the Full-prof software. We employed a data array obtained by the powder method using a Guinier-Huber image plate system. The chemical and phase compositions of the samples were determined using a Ziess Supra 55VP scanning electron microscope and an EMPA energy dispersive X-ray analyzer. The electronic structure was calculated by the Korringa–Kohn–Rostoker (KKR) technique in the coherent potential approximation (CPA) and local density approximation (LDA), as well as the full-potential linearized plane wave (FP-LAPW) method within density functional theory (DFT). In the calculations, we used experimental values of the lattice constant on a k grid 10×10×10 in size and the Moruzzi–Janak–Williams exchange-correlation potential parametrization. The width of the contoured energy window was 16 eV. The number of energy values for DOS calculations was 1000. To predict the behavior of the Fermi level, band gap, and electrokinetic characteristics of n-HfNiSn doped with Eratoms, the electron density distribution (DOS) was calculated. The calculated results pretending to be adequate to experimental studies should account for complete information on the semiconductor’s crystalline structure. To obtain more accurate results, we calculated the DOS for almost all possible cases of the mutual substitution of atoms at sites of the HfNiSn unit cell. Shows the result most consistent with experimental data. It was found that the disordered structure (Hf1-xNix)NiSn, x = 0.01, of the HfNiSn compound is most probable. We note that the same result was obtained from structural studies of HfNiSn. The partial (to 1 at %) substitution of Hf atoms with Ni atoms generates donor-type structural defects in the crystal, and the Fermi level is in the band gap which becomes narrower. It was also found that the minimum in the dependence of variations in the DOS at the Fermi level (DOSF(x)) for the disordered structure (Hf1-xNix)NiSn of the HfNiSn compound corresponds to the (Hf0.99Ni0.01)NiSn composition. In this semiconductor model, the Fermi level is in the band gap which is εg ≈ 282 meV. The same question arises when analyzing the behavior of the dependences (x) and (x) in Hf1-xErxNiSn. For example, the (x) variation in the concentration range 0.02 ≤ x ≤ 0.10 shows that the modulation amplitude of the continuous energy bands of Hf1-xErxNiSn HDCSs increases. Indeed, the activation energies (x) increase from (x = 0.05) = 38.3 meV to (x) (x = 0.07) = 59.2 meV. As we already noted, such behavior is possible only when compensating electrons appear in the p-type semiconductor due to the ionization of donors whose appearance was not initially assumed. In Hf1-xErxNiSn samples, x > 0.05, the decrease in (x) indicates a decrease in the modulation amplitude of the continuous energy bands, which is possible only when the degree of compensation of Hf1-xErxNiSn decreases due to a decrease or termination of the generation of donor-type structural defects. Thus, the initial assumption that n-ZrNiSn doping with Er atoms by substituting Hf atoms is accompanied by the generation of only donor-type structural defects in the crystal does not allow consistent explanation of the behavior of the energy characteristics of Hf1-xErxNiSn HDCS. The variations in the activation energy of hopping conduction (x) and the modulation amplitude of the continuous energy bands (x) unambiguously prove the existence of a donor source in Hf1-xErxNiSn. Further, we will identify the possible mechanism for the appearance of donors. The series of studies on the crystalline structure, energy spectrum, and electro-kinetic parameters of the n-HfNiSn intermetallic semiconductor heavily doped with the Er impurity allowed determination of the variation in the degree of compensation of the semiconductor due to the generation of both structural defects of donor nature during the substitution of Hf atoms with Er atoms and defects of donor nature during the partial substitution of Ni sites with Snatoms. The n-HfNiSn crystalline structure is disordered, and the Hf site can be occupied by Ni to ~1 at %, which generates structural defects of donor nature in the semiconductor and explains the mechanism of its “a priori doping with donors”. The mechanism of the degree of compensation of the semiconductor as the result of the crystal structure transformation during doping, leading to the generation of structural defects of donor nature was established. The results of the electronic structure calculation are in agreement with experimental data and the Hf1-xErxNiSn semiconductor is a promising thermoelectric material. The results are discussed in the framework of the heavily doped and compensated semiconductor model by Shklovsky–Efros.Item Керування характеристиками термометричного матеріалу TiNiSn1-xGax(Видавництво Львівської політехніки, 2016) Крайовський, В.Досліджено енергетичні, кінетичні та магнітні характеристики термометричного матеріалу TiNiSn1-xGax у діапазонах:T = 80?1400 K, x=0.01?0.15 і напруженості магнітного поля H £ 10 кГс. Показано, що характеристики TiNiSn1-xGax чутливі до зміни температури і можуть бути основою для виготовлення чутливих елементів термоперетворювачів. The electron energy state, magnetic and transport characteristics of thermometric materials TiNiSn1- xGax were investigated in the 80?1400 K temperature range and at charge carriers concentration from x=0.01?0.15 and H £ 10 kGs. The material TiNiSn1-xGax is sensitive to the temperature change and could be used as the basis for the sensitive thermoelectric devices. We investigated the crystal structure, electron density of states (DOS) and the kinetic and energy characteristics of n-TiNiSn heavily doped with the Ga impurity. Samples were synthesized at the laboratory of the Institute of Physical Chemistry, Vienna University. The TiNiSn1-xGax crystal-lattice periods were determined by X-ray analysis with the use of the Full-prof software. We employed a data array obtained by the powder method using a Guinier-Huber image plate system. The chemical and phase compositions of the samples were determined using a Ziess Supra 55VP scanning electron microscope and an EMPA energy dispersive X-ray analyzer. The electronic structure was calculated by the Korringa–Kohn–Rostoker (KKR) technique in the coherent potential approximation (CPA) and local density approximation (LDA), as well as the full-potential linearized plane wave (FP-LAPW) method within density functional theory (DFT). In the calculations, we used experimental values of the lattice constant on a k grid 10 ? 10 ? 10 in size and the Moruzzi–Janak–Williams exchangecorrelation potential parametrization. The width of the contoured energy window was 16 eV. The number of energy values for DOS calculations was 1000. To predict the behavior of the Fermi level, band gap, and electrokinetic characteristics of n-TiNiSn heavily doped with the Ga impurity, the electron density distribution (DoS) was calculated. The calculated results pretending to be adequate to experimental studies should account for complete information on the semiconductor’s crystalline structure. To obtain more accurate results, we calculated the DoS for almost all possible cases of the mutual substitution of atoms at sites of the TiNiSn unit cell. Shows the result most consistent with experimental data. It was found that the disordered structure TiNiSn1-x-уGax, of the TiNiSn compound is most probable. We note that the same result was obtained from structural studies of TiNiSn. The partial (to 1 at %) substitution of Sn atoms with Ga atoms generates donor-type structural defects in the crystal, and the Fermi level is in the band gap which becomes narrower.. In this semiconductor model, the Fermi level is in the band gap which is εg ≈ 282 meV. The same question arises when analyzing the behavior of the dependences (x) and (x) in TiNiSn1-x-уGax. For example, the (x) variation in the concentration range 0.02 ≤ x ≤ 0.10 shows that the modulation amplitude of the continuous energy bands of TiNiSn1-x-уGax HDCSs increases. Indeed, the activation energies (x) increase from (x = 0.05) = 38.3 meV to (x) (x = 0.07) = 59.2 meV. As we already noted, such behavior is possible only when compensating electrons appear in the p-type semiconductor due to the ionization of donors whose appearance was not initially assumed. In TiNiSn1-x-уGax samples, x > 0.05, the decrease in (x) indicates a decrease in the modulation amplitude of the continuous energy bands, which is possible only when the degree of compensation of TiNiSn1-x-уGax decreases due to a decrease or termination of the generation of donor-type structural defects. Thus, the initial assumption that n-ZrNiSn doping with Ga atoms by substituting Ti atoms is accompanied by the generation of only donor-type structural defects in the crystal does not allow consistent explanation of the behavior of the energy characteristics of TiNiSn1-x-уGax HDCS. The variations in the activation energy of hopping conduction (x) and the modulation amplitude of the continuous energy bands (x) unambiguously prove the existence of a donor source in TiNiSn1-x-уGax. Further, we will identify the possible mechanism for the appearance of donors. The series of studies on the crystalline structure, energy spectrum, and electro-kinetic parameters of the n-TiNiSn intermetallic semiconductor heavily doped with the Ce impurity allowed determination of the variation in the degree of compensation of the semiconductor due to the generation of both structural defects of donor nature during the substitution of Sn atoms with Ga atoms and defects of donor nature during the partial substitution of Ni sites with Sn atoms. The mechanism of the degree of compensation of the semiconductor as the result of the crystal structure transformation during doping, leading to the generation of structural defects of donor nature was established. The results of the electronic structure calculation are in agreement with experimental data and the TiNiSn1-x-уGax semiconductor is a promising thermectric material. The results are discussed in the framework of the heavily doped and compensated semiconductor model by Shklovsky-Efros.Item Дослідження термометричного матеріалу Zr1-xCeNiSn(Видавництво Львівської політехніки, 2015) Крайовський, Володимир; Ромака, Володимир; Стадник, Юрій; Ромака, Любов; Андрій, ГориньДосліджено енергетичні, кінетичні та магнітні характеристики термометричного матеріалу Zr1-xCexNiSn у діапазонах: T = 80÷400 K, x=0.01÷0.10 і напруженості магнітного поля H £10 кГс. Показано, що характеристики Zr1-xCexNiSn чутливі до зміни температури і він може бути основою для виготовлення чутливих елементів термоперетворювачів. Исследованы энергетические, кинетические и магнитные характеристики термометрического материала Zr1-xCexNiSn в диапазонах: T = 80÷400 K, x=0.01÷0.10 и напряженности магнитного поля H £10 кГс. Показано,что характеристики Zr1-xCexNiSn чувствительны к изменениям температуры и он может быть основой для изготовления чувствительных элементов термопреобразователей. The electron energy state, magnetic and transport characteristics of of thermometric materials Zr1-xCexNiSn were investigated in the T = 80 ¸ 400 K temperature range and at charge carriers concentration from x=0.01÷0.10 and H £ 10 kGs. The material Zr1-xCexNiSn is sensitive to the temperature change and could be used as the basis for the sensitive thermoelectric devices. We investigated the crystal structure, electron density of states (DOS) and the kinetic and energy characteristics of n-ZrNiSn heavily doped with the Ce impurity. Samples were synthesized at the laboratory of the Institute of Physical Chemistry, Vienna University. The Zr1-xCexNiSn crystal-lattice periods were determined by X-ray analysis with the use of the Full-prof software. We employed a data array obtained by the powder method using a Guinier-Huber image plate system. The chemical and phase compositions of the samples were determined using a Ziess Supra 55VP scanning electron microscope and an EMPA energy dispersive X-ray analyzer. The electronic structure was calculated by the Korringa–Kohn–Rostoker (KKR) technique in the coherent potential approximation (CPA) and local density approximation (LDA), as well as the full-potential linearized plane wave (FP-LAPW) method within density functional theory (DFT). In the calculations, we used experimental values of the lattice constant on a k grid 10 × 10 × 10 in size and the Moruzzi–Janak–Williams exchange-correlation potential parametrization. The width of the contoured energy window was 16 eV. The number of energy values for DOS calculations was 1000. To predict the behavior of the Fermi level, band gap, and electrokinetic characteristics of n-ZrNiSn doped with Ce atoms, the electron density distribution (DoS) was calculated. The calculated results pretending to be adequate to experimental studies should account for complete information on the semiconductor’s crystalline structure. To obtain more accurate results, we calculated the DoS for almost all possible cases of the mutual substitution of atoms at sites of the ZrNiSn unit cell. Shows the result most consistent with experimental data. It was found that the disordered structure (Zr1-xNix)NiSn, x = 0.01, of the ZrNiSn compound is most probable. We note that the same result was obtained from structural studies of ZrNiSn. The partial (to 1 at %) substitution of Zr atoms with Ni atoms generates donor-type structural defects in the crystal, and the Fermi level is in the band gap which becomes narrower. It was also found that the minimum in the dependence of variations in the DoS at the Fermi level (DoSF(x)) for the disordered structure (Zr1-xNix)NiSn of the ZrNiSn compound corresponds to the (Zr0.99Ni0.01)NiSn composition. In this semiconductor model, the Fermi level is in the band gap which is εg ≈ 282 meV. The same question arises when analyzing the behavior of the dependences (x) and (x) in Zr1-xCexNiSn. For example, the (x) variation in the concentration range 0.02 ≤ x ≤ 0.10 shows that the modulation amplitude of the continuous energy bands of Zr1-xCexNiSn HDCSs increases. Indeed, the activation energies (x) increase from (x = 0.05) = 38.3 meV to (x)(x = 0.07) = 59.2 meV. As we already noted, such behavior is possible only when compensating electrons appear in the p-type semiconductor due to the ionization of donors whose appearance was not initially assumed. In Zr1-xCexNiSn samples, x > 0.05, the decrease in (x) indicates a decrease in the modulation amplitude of the continuous energy bands, which is possible only when the degree of compensation of Zr1-xCexNiSn decreases due to a decrease or termination of the generation of donor-type structural defects. Thus, the initial assumption that n-ZrNiSn doping with Ce atoms by substituting Zr atoms is accompanied by the generation of only donor-type structural defects in the crystal does not allow consistent explanation of the behavior of the energy characteristics of Zr1-xCexNiSn HDCS. The variations in the activation energy of hopping conduction (x) and the modulation amplitude of the continuous energy bands (x) unambiguously prove the existence of a donor source in HfNi1-xCеxSn. Further, we will identify the possible mechanism for the appearance of donors. The series of studies on the crystalline structure, energy spectrum, and electro-kinetic parameters of the n-ZrNiSn intermetallic semiconductor heavily doped with the Ce impurity allowed determination of the variation in the degree of compensation of the semiconductor due to the generation of both structural defects of donor nature during the substitution of Zr atomswith Ce atoms and defects of donor nature during the partial substitution of Ni sites with Sn atoms. The n-ZrNiSn crystalline structure is disordered, and the Zr site can be occupied by Ni to ~1 at%, which generates structural defects of donor nature in the semiconductor and explains the mechanism of its “a priori doping with donors”. The mechanism of the degree of compensation of the semiconductor as the result of the crystal structure transformation during doping, leading to the generation of structural defects of donor nature was established. The results of the electronic structure calculation are in agreement with experimental data and the Zr1-xCexNiSn semiconductor is a promising thermoelectric material. The results are discussed in the framework of the heavily doped and compensated semiconductor model by Shklovsky–Efros.Item Quantum-chemical calculation of modified iliconcontained zeolite clusters electronic structure by zinc and calcium ions(Publishing House of Lviv Polytechnic National University, 2014) Pokhmurskii, Vasyl; Korniy, Sergiy; Kopylets, Volodymyr; Kosarevych, BogdanGeometrical and electronic structure of clinoptilolite clusters modified by zinc and calcium cations were calculated by semiempirical quantumchemical method PM6. The value of formation heat, potentials of ionization, EHOMO and ELUMO energies, cations and oxygen atoms charges, and also binding energy of cations with the cluster were obtained. The redistribution of electronic density on the oxygen atoms of clusters during formation of bonds with zinc and calcium cations was analyzed. The ability of modified clinoptilolite clusters to sorb the hydrogen ions has been estimated. It has been established that clinoptilolite clusters modified by calcium cations can inhibit corrosive processes on the metals surface. Із використанням напівемпіричного квантово-хімічного методу PM6 проведені розрахунки геометричної та електронної структури модифікованих кластерів клиноптилоліту катіонами кальцію та цинку. Отримано значення теплот утворення, потенціалів йонізації, енергій EHOMO та ELUMO, зарядів на катіонах та кислотних центрах, а також енергії зв’язків катіонів з кластером. Проаналізовано перерозподіл електронної густини на атомах кисню кластерів під час утворення зв’язків з катіонами цинку та кальцію. Проведено оцінку реакційної здатності модифікованих кластерів клиноптилоліту до сорбції йонів водню. Встановлено, що модифіковані кластери клиноптилоліту катіонами кальцію можуть сповільнювати корозійні процеси на поверхні металів.