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Doped-BaGdInO4 is a promising material for many applications including solid oxide fuel cells due to its high oxide-ion conductivity. Here we employ atomistic simulations to show that the activation energy for oxygen migration in Ca-doped BaGdInO4 is lower as compared to undoped BaGdInO4 and importantly divalent doping will form oxygen vacancies. The results are consistent with recent experimental work that determined an increase in the diffusivity of Ca-doped BaGdInO4 as compared to the undoped case. Additionally, the most thermodynamically feasible defect in this material is the Gd[sbnd]In anti-site. Promising isovalent dopants on the Ba, Gd and In were found to be the Sr, Al and Sc respectively. The most favourable dopant on the Gd site to produce oxygen vacancies is Ca and its solution energy is lower only by 0.02 eV than that calculated for Sr. Ba2+ ion conduction in this material is slow with the migration energy barrier being higher than 2 eV. © 2021 Elsevier B.V.

Perovskite and perovskite related oxides are important materials with applications ranging from solid oxide fuel cells, electronics, batteries and high temperature superconductors. The investigation of physical properties at the atomic scale such as self-diffusion is important to further improve and/or miniaturize electronic or energy related devices. In the present review we examine the oxygen self-diffusion and defect processes in perovskite and perovskite related oxides. This contribution is not meant to be an exhaustive review of the literature but rather aims to highlight the important mechanisms and ways to tune self-diffusion in this important class of energy materials. © 2020 by the authors.

In the paper we describe the results of the structure formation and physicomechanical properties of WC-Co hard alloy from he standard especially fine-grained BK6-OM mixture of KZTS (Russia) in electrosintering (ES) process with the use of a constant electric current (I = 3000 A) in a graphite mold in vacuum under pressure of 40 MPa and temperatures above (1320°C) and below (1220°C) of the solidus line of phase diagram. For comparison, samples from this mixture are sintered according to the standard technology in vacuum. The advantage of ES in conditions of the solid phase interaction (1200°C) is shown for obtaining the two-phase structure of hard alloy with high-density, without signs of recrystallization of carbide grains, from the standard mixture of BK6-OM, which increases by 30 % the thermal conductivity, hardness, and fracture toughness compared to the Sun. The mechanism of destruction of the samples after ES in conditions of impact loading is established.

The process of plastic deformation of multicomponent ceramics based on the MAX phase at room temperature and at higher (1000 °C) temperature has been studied by dilatometry and microindentation. Based on the experimentally obtained dependence of the strain rate of the material on the magnitude of the applied load, conclusions were made about the mechanisms controlling the plastic deformation process in the samples under study.

Germanium is an important mainstream material for many nanoelectronic and sensor applications. The understanding of diffusion at an atomic level is important for fundamental and technological reasons. In the present review, we focus on the description of recent studies concerning n-type dopants, isovalent atoms, p-type dopants, and metallic and oxygen diffusion in germanium. Defect engineering strategies considered by the community over the past decade are discussed in view of their potential application to other systems. © 2019 by the authors. All right reserved.

The composition changes in the electroconsolidation of powdered ceramic materials based on SiC with Al₂O₃ and ZrO₂ contents are considered. Analyzed possible mechanisms of decrease of compaction ability due to chemical reactions and phase composition changes. The influence of nanodispersed powders on the formation of a eutectic composition during liquid-phase sintering and compaction of a material is shown. The nanocomposite material based on β-SiC, satisfying the requirements of a polyfunctional material obtained.

Oxygen–carbon defects have been studied for decades in silicon but are less well established in germanium. In the present study we employ density functional theory calculations to study the structure of the CiOi defect in germanium. Additionally, we investigate the interaction the CiOi defect with isovalent dopants such as silicon and tin. It is calculated that the CiOi defects will preferentially form near isovalent dopants in germanium. Interestingly the structure of the dopant-CiOi defects is different with the Sn residing next to the Oi whereas the Si atom bonds with the Ci. The differences in the structure of CiOi defects in the vicinity of isovalent dopants are discussed. © 2017, The Author(s).

Effect of electron irradiation on the excess conductivity of Y₁Ba₂Cu₃O₇₋δ single crystals is investigated. It is shown that irradiation with electrons leads to significant expansion of the temperature interval that excess conductivity exists. The excess conductivity Δσ(T) has been revealed to obey an exponential temperature dependence in he broad temperature range Tf < T < T*. The description of the excess conductivity can be interpreted in terms of the mean-field theory where T* is the mean-field ransition temperature to the pseudogap state and Δ*(T) is satisfactory described within the framework of the BCS-BEC crossover heory. The value of the transverse coherence length ξc(0) increases by a factor of 1.4 and the point of 2D-3D crossover shifts with respect to temperature.

Carbon constitutes a significant defect in silicon (Si) as it can interact with intrinsic point defects and affect the operation of devices. In heavily irradiated Si containing carbon the initially produced carbon interstitial-carbon substitutional (CiCs) defect can associate with self-interstitials (SiI's) to form, in the course of irradiation, the CiCs(SiI) defect and further form larger complexes namely, CiCs(SiI)n defects, by the sequential trapping of self-interstitials defects. In the present study, we use density functional theory to clarify the structure and energetics of the CiCs(SiI)n defects. We report that the lowest energy CiCs(SiI) and CiCs(SiI)2 defects are strongly bound with -2.77 and -5.30 eV, respectively. © 2018 by the authors.

The results of research of influence of structure and phase composition parameters on the microstructure, physico-mechanical and cutting properties of aluminum oxide-based composites obtained by electrosparking (electroconsolidation) are described. It has been established that formation of the composite structure due to introduction of SiC nanopowders into the micropowder of aluminum oxide makes it possible to improve the physical and mechanical properties and wear resistance of Al₂O₃ ceramics.

The paper discusses the conditionality of such physical properties of polycomponent oxygen-free ceramics (MAX phases), as thermal and fracture resistance, with a special physicochemical nature of the binding forces between the elements forming the MAX phase and with a specific structural state characterized by the presence of thin interlayer between the structure elements with an unordered arrangement of atoms. The results of the experimental study of some of the physical properties of Ti₃AlC₂-based materials are presented, which are consistent with the proposed concept.

It has been determined that carbon-oxygen-self-interstitial defects in silicon (Si) can influence the operation of devices through the concentration of intrinsic point defects. Doping with larger isovalent dopants such as germanium (Ge) and tin (Sn) can impact the formation, energetics and structure of defect clusters in Si. In the present study we use density functional theory calculations to gain insights on the formation and stability of the CiOi(SiI)n (n = 0, 1, 2) defects in Si doped with Ge or Sn. It is calculated that the CiOi(SiI)n defects will preferentially form away from the oversized dopants. This result for the interstitial clusters is opposite to what is expected for vacancy-containing clusters which strongly associate with oversized dopants. © 2017 Elsevier Ltd

Analysis of the kinetics of relaxation processes observed at room temperature in the ReBa₂Cu₃O₇₋ₓ (Re=Y, Ho) compounds, having a high-temperature superconductivity is made. It was concluded that the initial (faster) stage of these processes is controlled by a single-file diffusion of oxygen along one-dimensional chains of vacancies, forming in the oxygen sub-lattice of compound with a deficit of oxygen, and final (slow) stage controls by the usual classical diffusion. Presented and discussed the results of two-stage relaxation of the electrical resistance of above mentioned compounds which were a long time (more than three days) at room temperature in air.

Carbon–oxygen-self-interstitial defects in silicon (Si) are technologically important as they can impact the operation of devices through the concentration of intrinsic point defects. In irradiated Si the CiOi defect attracts self-interstitials (SiI’s) and leads to the formation of the CiOi(SiI). Experimental studies have determined that annealing at 150 °C results in the capturing of more SiI’s leading to the formation of the CiOi(SiI)2 defect. Recent experimental studies proposed that the CiOi(SiI)2 defect is bistable and considered possible configurations. In the present study we aim to clarify the structure of the CiOi(SiI)2 defect and use density functional theory calculations to gain insights on the formation and stability of the CiOi(SiI)2 defect in Si. It is calculated that two configurations are energetically favourable differing in energy by only 0.19 eV. © 2017, The Author(s).

The technological requirement to optimize materials for energy and electronic materials has led to the use of defect engineering strategies. These strategies take advantage of the impact of composition, disorder, structure, and mechanical strain on the material properties. In the present review, we highlight key strategies presently employed or considered to tune the properties of energy and electronic materials. We consider examples from electronic materials (silicon and germanium), photocatalysis (titanium oxide), solid oxide fuel cells (cerium oxide), and nuclear materials (nanocomposites). © 2017 by the authors.

In this work, we have investigated the effect of high pressure on conductivity in basal plane of the high temperature super conducting single crystals HoBa₂Cu₃O₇-δ with oxygen deficiency. It has been determined that the excess conductivity Δσ(T) of HoBa₂Cu₃O₇-δ single crystals in temperature interval near the critical temperature (Tc) is described within the framework of the Aslamazov-Larkin theoretical model. It has been shown that evolution of the transverse coherence length ξc(0) in the case of application/removal of the high pressure is largely determined by the "relaxation" pressure effect during prolonged exposure of the sample under load at the room temperature.

It has been determined experimentally that doping silicon with large isovalent dopants such as tin can limit the concentration of vacancy-oxygen defects, this in turn, can be deleterious for the materials properties and its application. These results have been supported by recent calculations based on density functional theory employing hybrid functional. In the present study, we employ mass action analysis to calculate the impact of germanium, tin and lead doping on the relative concentrations of vacancy-oxygen defects and defect clusters in silicon under equilibrium conditions. In particular, we calculate how much isovalent doping is required to constrain vacancy-oxygen concentration in silicon and conclude that Sn and Pb doping are the most effective isovalent dopants. The results are discussed in view of recent experimental and computational results. © 2016, Springer Science+Business Media New York.

Irradiation induced defects in silicon are technologically important as they impact the electronic properties. Calculations based on density functional theory employing hybrid functionals have been previously used to investigate the structures and relative energies of defect clusters formed between vacancies, self-interstitials, carbon and oxygen atoms in silicon. In this study we employ a model to calculate the relative concentrations of carbon related defects in silicon. It is calculated that the carbon content has a significant impact upon the concentration of carbon-related defects. The CiCs defect is the most populous for all the conditions considered followed by the CiOiSiI and the CiOi defects. CiOiSiI and the CiOi become increasingly important for silicon with high carbon concentrations. © 2016, Springer Science+Business Media New York.

In the present study influence of longitudinal magnetic field on temperature dependence of the excess conductivity in the temperature interval of transition to the superconducting state in untwinned YBa₂Cu₃O₇-δ single crystals with optimal oxygen content are investigated. Causes of low-temperature tails (paracoherent transitions) in resistive transitions in the superconducting state are analyzed in the framework of implementation of various regimes of the phase state of vortex matter.

We investigate the conducting properties of the optimally oxygen doped YBa₂Cu₃O₇₋δ single crystals in the basal ab-plane before and after a long time exposure (aging) at air atmosphere. Prolonged exposure leads to increase of amount of the effective scattering centers of the normal carriers. The excess conductivity in a wide temperature range has exponential temperature dependence and near the critical temperature (Tc) is well described within the Aslamazov-Larkin theoretical model. Here we show that the prolonged exposure leads to a great extention of temperature range of the pseudogap state implementation and to narrowing the linear section of the dependence ρab(T).

We investigate the impact of tin (Sn) doping on the formation and the thermal stability of the vacancy-oxygen (VO or A-center) in the electron-irradiated Czochralski silicon (Si) and its conversion to the VO 2 defects. Previous experimental studies are consistent with the viewpoint that Sn (and other oversized isovalent atoms) doping suppresses the formation of the A-center. The results are discussed in view of recent density functional theory calculations, whereas we employ mass action analysis to calculate the impact of isovalent dopants on the suppression of the A-center. We propose point defect engineering strategies to suppress the concentration of the deleterious A-centers in Si and in related materials such as germanium. © 2014 Springer Science+Business Media New York.

Effect of high hydrostatic pressure up to 17 kbar on conductivity of lightly Pr-doped Y₁₋xPrxBa₂Cu₃O₇₋δ (x~0.05) single crystals is investigated. We show that in contrast to non-doped YBa2Cu3O7-δ samples, application of the high pressure leads to a substantial increase of the pressure derivative of the coherence length dξc/dP and temperature shift of 2D-3D crossover point. Possible mechanisms of the influence of the high pressure on the critical temperature and the coherence length are discussed within the frames of a model assuming the presence of singularities in the charge carriers electron spectrum typical for lattices with strong coupling. The excess conductivity Δ σ(T) inY₀.₉₅xPr₀Ba₂Cu₃O₇₋δ has beenY0.95Pr0.05Ba2Cu3O7-δ revealed to obey an exponential dependence in the wide temperature range Tf < T < T*. At this, description of the excess conductivity by the expression Δ σ ~ (1 - T/T*)exp(Δ*ab/T) can be interpreted in terms of the mean-field theory, where T* is the mean-field superconducting transition temperature and pseudogap temperature dependence is satisfactory described within the framework of the BCS-BEC crossover theory. An increase of the applied pressure leads to narrowing of the temperature range of realization of the pseudogap regime, thereby expanding the linear temperature dependence of the basal-plane resistivity ρab(T).

The electrical resistivity in the range of Tc-300 K in the layer planes of YBa₂Cu₃O₇₋x single crystals with a range of oxygen deficiency, which is characterized by the Tc in the range 78 + 92 K was studied. The experimental data on the resistance in normal state are approximated by an expression that takes into account the scattering of electrons on phonons, as well as on defects and the fluctuation conductivity in 3D-model of the Aslamazov-Larkin theory. According to this approximation, depending upon the oxygen deficiency, the Debye temperature changes from 245 to 400 K, coherence length ξc(0) ≈ 0.5 Å .

Dynamics of the vortex matter in YBa₂Cu₃O₇₋δ single crystal with unidirectional twin boundaries was studied experimentally in a wide range of velocities of the magnetic flux in the tilted magnetic field. It was determined that with orientation of the magnetic field vector in the locality of ab-plane, the dynamics of the magnetic flux near the melting temperature of the vortex lattice can be described by the Kim-Anderson model and under temperature lowering by the theory of collective pinning on small-scale defects or by the vortex glass model. The intrinsic pinning caused by the layered crystal structure of the material has an impact on the dynamics of magnetic flux and this effect increases with the temperature decreasing.

The effect of a constant magnetic field to 12.7 kOe on the temperature dependences of electric conductivity of aluminum-doped YBaCuO single crystals with a system of unidirectional twinning boundaries has been investigated. It is determined that the twinning boundaries are effective centers of scattering of fluctuation carriers. Directly near Tc the temperature dependences of the excess paraconductivity are satisfactorily described by the Hikami-Larkin theoretical model of fluctuation conductivity for layered superconducting systems. The reasons for the suppression of three-dimensional superconducting fluctuations and the nonmonotonic dependence of ξc(0,H) in weak magnetic fields with the magnetic field vector oriented along c axis were discussed. It was shown that the lack of fan-shaped expansion of the resistive transitions in the magnetic field in these samples is conditioned by the lack of the no pinning vortex liquid phase due to increased pinning of the vortex lattice at the twin boundaries.

In the present study influence of praseodymium doping on conductivity across (transverse) the basal plane of high-temperature superconducting Y₁₋xPrxBa₂Cu₃O₇₋δ single crystals is investigated. It is determined that increase of praseodymium doping leads to increased localization effects and implementation of the metal – insulator transition Y₁₋xPrxBa₂Cu₃O₇₋δ, which always precedes the superconducting transition. The praseodymium concentration increase also leads to significant displacement of the point of the metal – insulator transition to the low temperature region.

The influence of high hydrostatic pressure on electrical resistance in afr-plane of oxygen underdoped Ho₁Ba₂Cu₃O₇₋δ has been studied. It was found that high-pressure-in-duced redistribution of labile oxygen leaded to increasing phase separation, which was accompanied by a process of structural relaxation and uphill diffusion in the bulk of the pilot sample. It has been suggested that the generation of low-temperature (oxygen-depleted) phase can occur at twin boundaries. The temperature dependence of the resistivity above Tc can be accurately approximated by the model s-d-electron scattering by phonons. Application of high pressure leads to a decrease of the resistance, which at high temperatures is much larger than at low temperatures. This may be due to the weakening the electron-phonon interaction with increasing pressure.

In this work we study an influence of the disorientation angle between direction of constant magnetic field up to 15 kOe and ah-plane α ≡ ∠(H,ab) on the temperature dependences of the excess conductivity in the temperature interval of transition to superconducting state in untwinned YBa₂CU₃O₇₋δ single crystals with a small oxygen hypostoichiometry. At temperature T > Tc, the temperature dependence of the excess para-conductivity is interpreted within the Aslamazov-Larkin theoretical model of the fluctuation conductivity for layered superconductors. The cause of appearances of low temperature "tails" (para-coherent transitions) on the resistive transitions, corresponding to different phase regimes of the vortex-matter state is discussed. Remove selected

Atomistic computer simulation techniques based on energy minimization have been employed to predict the equilibrium lattice parameters and volumes of a series of rare-earth sesquioxides and their polymorphs. The results have been found in agreement with experimental data and ab initio studies given in the literature. To demonstrate the applicability of the computational methodology the migration of lithium ions (Li⁺) in yttria (Y₂O₃) has been considered. Атомістичні методи комп’ютерного моделювання, основані на принципі мінімізації енергії, використані для прогнозування рівноважних параметрів і об’єма кристалічної гратки ряда рідкоземельних оксидів та їх поліморф. Результати моделювання знаходяться в доброму узгoдженні з експериментальними і літературними даними. Для демонстрації запропонованої обчислювальної методики розглянутo міграцію іонів літія (Li⁺) в оксиді ітрія (Y₂O₃). Атомистические методы компьютерного моделирования, основанные на принципе минимизации энергии, использованы для предсказания равновесных параметров и объема кристаллической решетки ряда редкоземельных оксидов и их полиморф. Результаты моделирования находятся в хорошем согласии с экспериментальными и литературными данными. Для демонстрации применимости предложенной вычислительной методики рассмотрена миграция ионов лития (Li⁺) в оксиде иттрия (Y₂O₃).

We report the results of defect structures studies of silicon implanted at different temperatures with Mn ions (Si:Mn) and of GaMnAs layers, next annealed under ambient and high pressures. An influence of annealing conditions on structural properties of Si:Mn and GaMnAs layers was investigated. It has been confirmed that annealing of the Si:Mn samples after implantation results in crystallization of silicon inside the buried postimplanted layer, as well as in the formation of ferromagnetic Mn4Si7 precipitates. A change of strain in the GaMnAs layer, from the compressive to the tensile one, related to a creation of nanoclustered MnAs, was found to be dependent on processing conditions and primary existing structural defects, while independent of the Mn concentration. An influence of primary defects on the structural transformations of the GaMnAs layer is discussed. Атомістичні методи імітаційного моделювання, основані на принципі мінімізації енергії, використані для вивчення структурних параметрів ряду орторомбічних R1–xPrxBa2Cu3O6.5 і пов'язаних з ними сполук. Нові міжатомні потенційні параметри взаємодії одержані для широкого діапазону оксидів, таких як CuO, R2O3, RBa2Cu3O6.5 і R1–xPrxBa2Cu3O6.5 (всього 62 сполуки). Одержані дані знаходяться в доброму узгoдженні з попередніми результатами експериментальних і теоретичних досліджень. Мета даної роботи – прогнозування решіточних потенціалів взаємодії, що можуть бути надалі використані як основа для теоретичного вивчення дефектної хімії надпровідних купратів та інших технологічно важливих оксидів.

Studied has been the effect of oxygen deficiency as well as of a low (up to 5 %) Al and Pr doping on conductivity in the basis plane of the ReBa₂Cu₃O₇₋δ (Re=Y, Ho) HTSC single crystals. The excess conductivity Δσ(T) of the studied samples has been found to show an exponential character in a wide temperature range Tf

We present the results of transport study of vortex dynamics in YBa₂Cu₃O₆.₈₇ crystals in the magnetic field H||c. In low magnetic fields, H

The conductivity in the basis plane of YBa₂Cu₃-yAlyO₇₋δ single crystals with a pre-specified topology of plane defects has been investigated. The results indicate that the doping with Al results in increased number of the effective scattering centers of the normal carriers. The excess conductivity for the analyzed single crystals within a wide temperature interval corresponds to an exponential temperature dependence. Near Tc, it is described well by the Aslamazov-Larkin theoretical model. A partial substitution of Cu with Al results in a considerable expansion of the temperature interval of pseudo-gap anomaly existence in the ab-plane.

The effect of the fluctuation paraconductivity in optimal oxygen-doped ReBa₂Cu₃O₇₋δ (Re = Y, Ho) single crystals has been investigated. The results indicate that the theoretical model of Aslamazov–Larkin (AL) describes the temperature dependence of fluctuation paraconductivity (FP) near the critical temperature (Tc). At temperatures above the temperature of the 2D−3D crossover this dependence is appropriately described by the Lawrence–Doniach (LD) theory. The extended linear dependence of ρab(Т), in the crystal with the minimum critical temperature indicates that we have a high defect concentration in this sample. This in turn causes negative processes into forming fluctuation pairs.

The temperature dependences of the conductivity along and across the basis plane have been measured in YBa₂Cu₃O₇₋ₓ single crystals with different oxygen non-stoichiometry. In the oxygen-deficit samples, an inhomogeneous oxygen distribution within the crystal bulk is found, that results in the formation of phases with different critical of superconducting transition temperatures. The accordance of the experimental results with the predictions of different theoretical models has been considered. It has been revealed that the anisotropy of the normal resistivity pc/pab(T) is described well using the universal "law of 1/2", for thermal activation of the hopping conductivity.

We have investigated the evolution of the temperature dependence of the in-plane and off-plane conductivity of YBa₂Cu₃O₇₋δ single crystals due to the decrease of the oxygen content in the samples caused by a heat treatment. The concentration dependence of the in-plane and off-plane energy gaps has been determined. It has been shown that the enhancement of the localization effects results in a suppression of the pseudogap state. At the same time, the decrease of the oxygen content results in a relative narrowing of the temperature interval in which the regime of the fluctuating conductivity is realized.

Evolution of the excess conductivity in Y₁Ba₂Cu₃O₇-δ single crystals has been studied under stepwise oxygen removal by heat treatment. The concentration dependence of the coherence length along С axis εc(0) on the oxygen content has been obtained. The oxygen content reduction from δ ≤ 0.1 to δ ≈ 0.23 has been shown to result in a substantial broadening of the temperature interval where the excess conductivity takes place. The εc(0) value increases more than twice and the 2D-3D crossover point is shifted in temperature. Дослiджено еволюцiю надлишкової провiдностi монокристалiв Y₁Ba₂Cu₃O₇-δ при поетапному видаленнi кисню шляхом термообробки. Отримано концентрацiйну залежнiсть довжини когерентностi у напрямку осi с εc(0) вiд вмiсту кисню. Показано, що зменшення вмiсту кисню вiд δ ≤ 0.1 to δ ≈ 0.23 зумовлює значне розширення температурного iнтервалу iснування надлишкової провiдностi. При цьому величина εc(0) збiльшується бiльш нiж у два рази та змiщується за температурою точка 2D-3D кросоверу. Исследована эволюция избыточной проводимости монокристаллов Y₁Ba₂Cu₃O₇-δ при поэтапном удалении кислорода путем термообработки. Получена концентрационная зависимость длины когерентности в направлении оси с εc(0) от содержания кислорода. Показано, что понижение содержания кислорода от δ ≤ 0.1 to δ ≈ 0.23 приводит к значительному расширению температурного интервала существования избыточной проводимости. При этом величина εc(0) увеличивается более чем в два раза и смещается по температуре точка 2D-3D кроссовера.