The temperature dependences of electrical resistance were measured four-probe method. The analysis of the continuous structural evolution of the YBa2Cu3Oy superconductor using low-temperature X-ray diffraction have been performed. In the normal state, the dependences of the temperature coefficients of electrical resistance (αρ) on the volumetric thermal expansion (αV) are close to linear with correlation coefficients (correspondence) r 0.98. In the region of the transition to the superconducting state, the temperature dependences of αρ and αV exhibit anomalies in the form of maxima and minima of the functions. For each phase, the onset of the superconducting transition is accompanied by lattice compression, after which the volume grows in the region of the Tc value of these phases on the dρ/dT dependence. In the region of transition to the superconducting state, significant changes in the degree of orthorhombicity are observed, in the form of its sharp increase to 0.01 and 0.009 at temperatures of 90 and 87 K, respectively. It is shown that the volume change ΔVs in the temperature region from 92 to 90.5 K is higher than for the interval from 88 to 87 K and amounts to 0.73

A series of experiments has been performed to study the effect of plasma flows of argon, nitrogen, and their mixture with oxygen, produced by a dc plasmatron with an expanding channel of the output electrode, on the surface of nanostructured YBa2Cu3O _7-δ (YBCO) ceramics. Nanostructured ceramics S1, S2, S3, and S4 have been fabricated from YBCO powders synthesized by the sol‒gel method, followed by the heat treatment at 350°С (1 h), 910°С (20 h), and 700°C (10 h), with the following densities: ρ1 = 3.5, ρ2 = 5.5, ρ3 = 5.6, and ρ4 = 4.5 g/cm3. The surface morphology and Raman spectra of the superconducting nanostructured ceramics have been investigated before and after exposure to a plasma flow. It has been established that this exposure causes a surface modification in the form of compaction and recrystallization, as well as changes in the oxygen ordering in the structure. Molten monolithically conjugated grains have been found.

The temperature dependences of the electrical resistivity of the Ti 67 Al 33 intermetallic compound in the temperature range of 300–1000 K are presented, showing a change in the type of conductivity in this temperature range. It is shown that the electrical resistivity is able to return to an equilibrium state after various types of heat treatment consisting in cooling from high temperatures at rates from 1000 to 0.2°/min. It is shown that the alloy Ti 67 Al 33 has the property of “resistivity memory.”

Аннотация.На основе установленной корреляции между экспериментальными данными температурных зависимостей атермического фононного теплосопротивления и коэффициента объемного расширения полупроводников и диэлектриков, в том числе претерпевающих инверсию знака ангармонизма, дана интерпретация конечности фононной теплопроводности этих материалов.Константа, связывающая эти параметры, представляет собой предельное характеристическое теплосопротивление для каждого материала.Микроскопическая расшифровка этой константы дана на основе представлений о формировании кинетических коэффициентов в рамках концепции как Дебая, так и Максвелла.Показано, что в квазистатическом процессе особенности формирования теплопроводности, связанные с ангармонизмом колебаний, определяются температурной зависимостью относительной свободной энергии при переходе системы из одного равновесного состояния в другое.Результаты, приведенные в работе, могут быть востребованы для

Titanium–vanadium oxide (TixVyOz) nanofilms were prepared by atomic layer deposition using TiCl4, VOCl3, and water. The film growth was monitored in situ by quartz crystal microbalance. At a deposition temperature of 115°С, the films grew linearly with number of deposition cycles, and the surface reactions of the precursors were self-limiting. Films of two compositions, Ti0.9V0.1O3 and Ti0.5V0.5O3, were prepared; their density was 3.5 and 3.3 g cm–3, respectively. The content of Cl impurities in the films obtained was less than 0.2 at. %, the coating roughness was ~4.0 Å, and the band gap was 3.05 and 2.85 eV for Ti0.9V0.1O3 and Ti0.5V0.5O3, respectively. All the films obtained were amorphous. The heat treatment of the Ti0.5V0.5O3 film in air led to the formation of heterostructural TiO2–V2O5 coatings. At 450°С, nanostructures consisting of anatase TiO2 and nanorods of microcrystalline V2O5 were formed. An increase in the annealing temperature to 500°С led to increase in the length of V2O5 nanowires to tens of micrometers and to their separation from the substrate, and after annealing at 550°С the substrate surface was uniformly coated with nanoparticles. The films obtained in this study can find use in the development of catalysts and power storage systems.

A study is performed of the thermal atomic layer deposition (ALD) of molybdenum oxide (MoOx) films using MoOCl4 and H2O and titanium–molybdenum oxide (TixMoyOz) thin films using TiCl4, MoOCl4, and H2O. Film growth is investigated via in situ quartz crystal microbalance (QCM) in the 115 to 180°C range of temperatures. ALD processes are considered for TixMoyOz films with different ratios of TiCl4–H2O and MoOCl4–H2O subcycles in a supercycle. The linear growth of a film upon an increase in the number of ALD cycles is in all cases established. The surface reactions of halides and H2O are shown to be of a self-limiting. The QCM data show the considered surface chemistry can be used for depositing thin MoOx and TixMoyOz films. Fields of potential application of these thin films a catalysis, electrochromic devices, lithium-ion batteries, antibacterial coatings and others.

Nanostructured ceramics of the composition Bi 0.95 La 0.05 FeO 3 were fabricated, and the structure was studied before and after exposure to an argon plasma flow at a temperature of ∼ 600 °C for ∼ 30 minutes. Plasma treatment of the surface, with a positive effect of the formation of a monolithically conjugated structure and an increase in the size of grain crystallites, leads to a decrease in the proportion of the main phase on the surface to ∼70%. It has been established that compaction is up to ∼30% of the sample thickness.

In this study, a linear relationship between the doping level (p) and the temperature coefficient of electrical resistance (TCR) is shown and substantiated for 20 nanostructured superconducting ceramics based on YBa2Cu3O7-δ (YBCO). Variations of ceramic production parameters, ceramic particles' porosity and dispersion, average values of oxygen index or the normal phase conductivity type (metallic or semiconducting) do not violate this dependence. A distinctive feature of these ceramics is the decomposition of YBCO main superconducting phase into superconducting phases with different oxygen stoichiometries during nanostructuring. The values of p and ТCR and the change in the width of the superconducting transition (ΔTc) associated with this decay were obtained in situ by studying the temperature dependence of the resistance of each sample. The correlations between p and ТCR with ΔTc are shown. Slater's theory of elementary charge excitations formation in condensed medium, which is a system of interacting polarized ions and atoms, was used for interpretation of relationship between p and TCR established on the basis of these correlations.

The structure and properties of superconducting nanostructured ceramics YBa 2Cu 3O7-y (YBCO) before and after exposure to a plasma flow consisting of a mixture of argon and oxygen (at ∼ 600 °C for ∼ 1 min) are investigated. Plasma surface treatment, in addition to compaction of grains, leads to a change in the oxygen stoichiometry index and average crystallite size, as well as to a decrease in the proportion of the superconducting phase in the ceramic. After plasma treatment of ceramics, the character of the temperature dependence of the electrical resistance ρ = f (T) changes from metallic to semiconductor, and the temperature T c, onset remains constant.

On the basis of experimental studies (in situ) of the electrical resistance and thermal expansion of the Ti67 Al33 intermetallic compound in a metastable and stabilized state, the relationship between the temperature coefficients of athermal electrical resistance (TCAR) and thermal expansion (TCE) is shown. This relationship is universal because it is preserved under transitions from one state to another. The anomalies associated with the competition between the metallic and semiconducting types of conductivity observed in the TCAR, TEC and heat capacity curves coincide in temperature.

Изготовлены порошки с номинальным содержанием фазы YBCO и оптимально насыщенные кислородом методом твердофазного синтеза с использованием оксидов Y 2 O 3 , BaCO 3 и CuO.Спекание образцов проводилось в температурном и временном интервале от 900 до 936 ºС в 7 этапов в течение ~10-25 часов на каждом этапе.Проведены комплексные исследования структуры, морфологии и спектров комбинационного рассеяния.Изготовленные образцы преимущественно обладают орторомбической сверхпроводящей фазой с высоким содержанием кислорода.Максимальное содержание соединения YBa 2 Cu 3 O 7-(до ~95 %) достигалось после спекания при 936 ºС.Спектры комбинационного рассеяния демонстрируют характерные для состава YBCO колебательные моды: режим O(4)-A g в интервале от ~479 до ~496 см -1 ; режим O(2, 3)-A g в области от ~436 см -1 до ~447 см -1 ; режим O(2, 3)-B lg в интервале от ~307.5 см -1 до ~334 см -1 .Выполнены оценки содержания кислорода в образцах различными методами.Установлено, что концентрация кислорода в межгранульных средах оказалась ниже в среднем на ~5 %, чем в объеме.

Показана связь процессов возникновения и релаксации элементарных зарядовых возбуждений с особенностями изменения параметров кристаллической структуры YBa 2 Cu 3 O 7- (YBCO), которые обусловлены не только степенью дырочного допирования, но и снижением температурной хаотизации -ангармонизма колебаний атомов в среднем по решетке.Исследования основаны на теоретических представлениях и сведениях, следующих из анализа эмпирических данных и признанных положений о проводимости материалов.Подробно рассмотрены структура элементарных ячеек YBCO в трех основных модификациях, соответствующих стехиометриям с кислородными индексами 7- = 6; 6.5 и 7, а также заряды, приобретаемые базовыми блоками и блоком проводимости при чисто ионных связях между атомами в этих блоках.Рассматривается вопрос поставки дырок в плоскости Cu(2)O( 2)O(3) из цепи Cu(1)O(1) в результате относительных смещений ионов вдоль оси с ввиду возникновения эффекта диэлектрического экранирования.Показано, что локальные и обобществленные зарядовые возбуждения, обеспечивающие этот эффект, способны откликаться на внешнее воздействие подобно фермиевским электронам в металлах.Рассматриваются дрейфовая и диффузионная проводимости в YBCO такими элементарными зарядовыми возбуждениями, поскольку у него нее «свободных» носителей заряда, как в металлах и полупроводниках.Показано, что противоречие, связанное с прямой и обратной зависимостью времени релаксации от проводимости в рамках дрейфовой и диффузионной концепций не возникает, если учесть термическую объемную деформацию решетки, чем обычно пренебрегают при теоретической интерпретации.

Структура и свойства сверхпроводящей пленкисостава YBCO/SiO 2

Experimental study of thermal coefficients of both electrical resistance and volume expansion in nanostructured superconducting ceramics YBa 2 Cu3O 7 -8 and intermetallic Ti 67 Al 33 alloy was performed. In both compounds we found a correlation between the temperature dependences of these coefficients. Formation and relaxation of charge excitations in conductors with a nonmetallic type of interatomic bonds are discussed. We point that, to explain temperature dependence of the conductivity, one should take into account an anharmonicity of atomic vibrations.

The paper presents the results of a study of the surface structure of nanostructured superconducting ceramics YBa2Cu3O7-y (YBCO) before and after short-term exposure to a plasma stream. Exposure to the plasma stream changes the structure of the ceramic surface and the oxygen content in it, and also slightly increases the average crystallite size.