Low Impurity Concentration Research Articles

A new targetry system for production of zirconium-89 radioisotope with Cyclone-30 cyclotron

Abstract In this study, an efficient method for targetry and production of zirconium-89 radioisotope (89Zr) with Cyclone-30 cyclotron was developed. The preparation of a highly pure compressed yttrium oxide target material and design of a target made by copper for better heat transfer was performed. Electrodeposition of target with gold was done to prevent the entry of metallic impurities (copper, zinc and other trace metal elements). Nuclear reaction cross sections for optimization of production with new target and irradiation parameters of the target were evaluated. The prepared 89Zr in the form of [89Zr] Zr-oxalate had high radionuclidic purity (>99.9%) and a low chemical impurity concentration (<0.1 ppm for copper and zinc elements). The yield of 89Zr radioisotope production via the reaction of 89Y(p,n)89Zr was measured to be 77 ± 9.5 MBq/μAh (time of irradiation = 3, the current 20–30 µA). [89Zr] Zr-oxalate specific-activity was in the range 2.319641 × 104–3.479443 × 104 MBq/mmol of Oxalate.

Electrochemical extraction of rubidium from salt lake by using cupric ferrocyanide based on potassium shuttle

Extracting rubidium from high reserve salt lakes has been an important measure to cope with the growing demand for rubidium. However, due to the low concentration and high impurity ions in the salt lake, there was no rational method to extract rubidium. Prussian blue and its analogues (PBAs) with specific functional structures have shown good cycling stability for K+ and Rb+ with large ionic radii in the field of batteries and their special affinity (Li+ > Na+ > K+ > Rb+) for rubidium, which provides a new idea for the extraction of rubidium from salt lakes. In this paper, the cyclic electrochemical performance of synthesized copper ferricyanide (Cu3[Fe (CN)6]2) for rubidium was tested. Furthermore, a new method of rubidium extraction from salt lake was proposed by using potassium as the shuttle ion. The (K2Cu3[Fe (CN)6]2) obtained by intercalating K+ into copper hexacyanoferrate (Cu3[Fe (CN)6]2) with the electrochemical method was used to extract rubidium from simulated brine and the separation coefficients βRb: K, βRb: Na, βRb: Ca and βRb: Mg were 63, 1635, 585 and 2543, respectively. After that, rubidium was deintercalated by electrochemical oxidization of Rb2Cu3[Fe (CN)6]2 and the deintercalated efficiency can be reached 98 %. Rubidium enrichment can be achieved by repeating the above process with regenerated materials.

Computer model of track biosensor

Being based on the known model of a cylindrical nanopore created using the classical method of molecular dynamics, we have studied the patterns of electrolyte flow passing through a nanocylinder, which is used to simulate an ion-induced track in a thin film. In this study, the nanotrack model takes into account the defect structure of the nanotracks inner surface. A model of a structural defect, which is an adsorption center for model particles passing through a nanocylinder, has been described. It was revealed the sensitivity of the electrolyte flux density to its composition, which is explained by interaction of particles passing through the nanocylinder with structural defects of its inner surface. This effect enables to create a biosensor system for detecting the low concentration of impurities of various types in liquid.

Physical and mechanical properties of ultrapure copper obtained by zone melting

This paper presents the results of studies on the electrical conductivity, macro- and microstructure of ultrapure copper (5N3) obtained after zone melting of refined copper (99.96% Cu). The effect of residual concentrations of impurity metals on the electrical conductivity of ultrapure copper has been established. To assess the effect of low concentration impurities on the electrical conductivity of copper, the authors used a linear dependence of the increase in resistivity on the concentration of impurities (Ci), which was determined by the Mathyssen-Fleming rule. It is shown that low residual concentrations of impurity metals obtained in copper after its zone melting refining, ppm (ppm = 10–4 %): 0.2As; 0.06Sb; 0.006Ag; 0.07Bi; 0.006Sn; 0.02Pb; 1,1Ni have practically no effect on the electrical conductivity of ultrapure copper. The maximum electrical conductivity of M00K industrial grade copper (99.99% Cu) is 59 MSm/m, while zonerefined copper with a copper content of 99.999% has the electrical conductivity of 60.2 MSm/m. The values of the electrical conductivity of the obtained samples can serve to control the quality of obtained copper. It is shown that, in contrast to the microstructure of the initial copper sample, the ultrapure copper microstructure is a densely packed structure consisting of fine grains. On the microstructure map of ultrapure copper, the presence of individual impurity metals in the form of rounded small balls was established. Elongated filaments in the form of continuous lines, which are associated with the formation of chemical compounds of impurity metals with each other, are also found. This phenomenon is clearly observed on the microstructure map of ultrapure copper, captured at a magnification of 1000x under conditions of etching of the sample under study. The values of macro- and microhardness of the initial copper sample and ultrapure copper sample are established. The hardness of the initial copper sample is 84.42 HB (according to Brinell). After zone melting refining of copper from impurities, the hardness of the resulting ultrapure copper was 59.85 HB. Measurements of the microhardness of samples of the initial copper sample and ultrapure copper obtained by zone melting showed the microhardness of 103.0 and 70.42, respectively.

Analysis of the Efficiency of Technologies for Extraction Carbon Dioxide from Combustion Products

The main purpose of the article is to compare and analyze existing technologies for extracting carbon dioxide from combustion products in relation to mini-CHP plants operating on local fuels. The article presents a brief overview of the main technical features of the implementation of carbon dioxide extraction technologies from gas mixtures. The specific features and limitations for each of the methods are shown. Mathematical modeling of technological processes of adsorption, physical and chemical absorption is carried out on the basis of Aspen Hysys and Aspen Adsorption software packages. When modeling absorption processes, the composition of combustion products characteristic of the actual operating conditions of an energy source on wood chips was considered, while for the adsorption process, the composition of combustion products was simulated by a binary mixture of carbon dioxide and nitrogen with a molar content of 11 and 89 %, respectively. The results of numerical research that were obtained have shown that the highest degree of carbon dioxide extraction from combustion products is 97 %, and it is achieved in the optimal mode of implementation of chemical absorption technology. With the same method, the highest degree of purity of the resulting carbon dioxide is observed, viz. 86 % taking into account water vapor and 99 % if it is dry. The least effective technology for extracting carbon dioxide was the method of physical absorption in a fixed bed, in which the degree of purity of the resulting dry carbon dioxide was 79 %. Therefore, for practical use in the deep utilization of combustion products of mini-CHP plants operating on local fuels, to obtain carbon dioxide with a low content of impurities, it is necessary to apply the method of chemical absorption. The use of physical absorption technology in a fixed bed can be used to reduce energy source emissions or in cases where the degree of purity of carbon dioxide does not matter.

A facile process to optimize performance of regenerated Nd-Fe-B sintered magnets: Chemo-selective dissolution washing

In this work, the recycled Nd-Fe-B powders and regenerated Nd-Fe-B sintered magnets with low impurity content were successfully prepared from Nd-Fe-B magnet sludge via reduction diffusion (RD) method followed by a chemo-selective dissolution washing process. The chemo-selective dissolution effect of various solution (deionized water, dilute acetic acid solution, NH4Cl-methanol solution) was evaluated by impurity content and magnetic properties of the recycled Nd-Fe-B powder. The NH4Cl-methanol solution can selectively remove impurities with minimal damage to the magnetic phase. Besides, the optimal NH4Cl concentration and liquid-to-solid ratio were investigated. As a consequence, the contents of Ca, O, and H after optimal washing process are reduced to 0.07 wt%, 0.31 wt% and 0.22 wt%, respectively. Hence, M3 T is increased to 146.72 emu/g, which is 33% higher than that of the initial sludge. Then, the regenerated Nd-Fe-B sintered magnets with properties of Br = 11.66 kG, Hcj = 16.49 kOe, and (BH)m = 31.78 MGOe were successfully prepared by mixing with 40 wt% Nd4Fe14B alloy powders. Compared with the corresponding regenerated magnets washed with deionized water, the remanence and coercivity are increased by 18% and 59%, respectively.

Efficient narrow-band red-light-emitting diodes based on ambipolar organic single crystals

Organic single crystals have attracted immense attention in the field of organic light-emitting devices (OLEDs), owing to their unique advantages of long-range molecular ordering, high carrier mobility, high fluorescent quantum yield and low impurity content. Development of high-performance organic single crystal-based OLEDs with narrow-band emission is critical for high-purity displaying, yet it is still a major challenge to obtain a crystal-based OLED with both narrow fullwidth at half maximum (FWHM) and high electroluminescence (EL) performance. Here, molecular doping engineering is employed by taking 2,6-diphenylanthracene (DPA) as host crystal and pentacene (Pen) as red guest emitter material. 2,2′-Bis[4-(trifluoromethyl)phenyl]-5,5′-bithiazole (BTPB) with strong electron-withdrawing ability are further doped for the growth of ambipolar crystals in order for balanced hole and electron mobility. As a result, DPA: 3% Pen: 15% BTPB crystal-based OLEDs exhibit a maximum luminance and current efficiency of 10,850 cd m −2 and 2.3 cd A −1 , respectively, and an EQE of 1.95%. The obtained red-light-emission with a narrow FWHM increases high color purity of crystal-based OLEDs. It demonstrates that high-performance crystal-based OLEDs with narrow-band emission are of great significance for the development of organic electronics, especially for display and lighting applications. Molecular doping engineering is employed by taking DPA single crystals as host matrix and pentacene as red guest emitter. BTPB with strong electron-withdrawing ability is further doped for obtaining ambipolar crystals. DPA: 3% Pen: 15% BTPB crystal-based OLEDs exhibit a red-light-emission with a narrow FWHM and high-efficiency, which are of great significance for the development of organic single crystal-based electronics. • Doping of pentacene into host DPA crystal enable narrow-band red-light-emission. • Ambipolar crystals obtained by doping N -type BTPB for balanced charge mobility. • Narrow-band EL emission from crystal-based OLEDs increases a high purity. • DPA: 3% Pe: 15% BTPB crystal-based OLEDs exhibit the highest EL performance.

Atomic layer deposition of MoNx thin films using a newly synthesized liquid Mo precursor

Molybdenum nitride thin films are deposited using a newly synthesized liquid Mo precursor [MoCl4(THD)(THF)] in an ALD super-cycle process. The new precursor is synthesized using MoCl5 and 2,2,6,6-tetramethyl-3,5-heptanedione, which is a bidentate ligand. The synthesized precursor exists in the liquid phase at room temperature and has a characteristic of evaporating 99% at 150–220 °C. Using this new precursor in an ALD super-cycle process results in a pure MoNx thin film with few impurities (C and O). In addition, such MoNx thin films have relatively low resistivity values due to excellent crystallinity and a low impurity concentration. The films' diffusion barrier characteristics confirm that they can perform the role of a barrier at over 600 °C.

Temperature study of atmospheric-pressure plasma-enhanced spatial ALD of Al2O3 using infrared and optical emission spectroscopy

Atmospheric-pressure plasma-enhanced spatial atomic layer deposition (PE-s-ALD) is considered a promising technique for high-throughput and low-temperature deposition of ultrathin films for applications where volume and costs are particularly relevant. The number of atmospheric-pressure PE-s-ALD processes developed so far is rather limited, and the fundamental aspects of their growth mechanisms are largely unexplored. This work presents a study of the atmospheric-pressure PE-s-ALD process of Al2O3 using trimethylaluminum [TMA, Al(CH3)3] and Ar–O2 plasma within the temperature range of 80–200 °C. Thin-film analysis revealed low impurity contents and a decreasing growth-per-cycle (GPC) with increasing temperature. The underlying chemistry of the process was studied with a combination of gas-phase infrared spectroscopy on the exhaust plasma gas and optical emission spectroscopy (OES) on the plasma zone. Among the chemical species formed in the plasma half-cycle, CO2, H2O, CH4, and CH2O were identified. The formation of these products confirms that the removal of CH3 ligands during the plasma half-cycle occurs through two reaction pathways that have a different temperature dependences: (i) combustion reactions initiated by O2 plasma species and leading to CO2 and H2O formation and (ii) thermal ALD-like reactions initiated by the H2O molecules formed in pathway (i) and resulting in CH4 production. With increasing temperature, the dehydroxylation of OH groups cause less TMA adsorption which leads to less CO2 and H2O from the combustion reactions in the plasma step. At the same time, the higher reactivity of H2O at higher temperatures initiates more thermal ALD-like reactions, thus producing relatively more CH4. The CH4 can also undergo further gas-phase reactions leading to the formation of CH2O as was theoretically predicted. Another observation is that O3, which is naturally produced in the atmospheric-pressure O2 plasma, decomposes at higher temperatures mainly due to an increase of gas-phase collisions. In addition to the new insights into the growth mechanism of atmospheric-pressure PE-s-ALD of Al2O3, this work presents a method to study both the surface chemistry during spatial ALD to further extend our fundamental understanding of the method.

Analysis of the use of magnesium-containing additives in the charge of iron flux in order to reduce CO2 emissions

The growing requirements for the quality of finished steel products oblige to obtain steel with a low content of harmful impurities, especially sulfur. The main charge for steel production in the conditions of JSC EVRAZ NTMK is vanadium iron, the external desulfurization of which leads to large losses of valuable vanadium. Therefore, the smelting of iron with a low sulfur content is an urgent task. The main way to reduce sulfur in iron is to increase the basicity of the slag (B2), but MgO is the best desulfurizer. The paper evaluates the effectiveness of the use of various magnesium-containing materials in the conditions of the blast-furnace stage of JSC EVRAZ NTMK, taking into account CO2 emissions. The possibility of replacing limestone in the iron flux charge with dolomite, as well as with steel converter slag, is considered. Both materials will increase the proportion of MgO in blast-furnace slag, however, the use of dolomite is accompanied by a two-fold increase in CO2 emissions compared to limestone. Converter steel slag (CSS) does not contain carbonates, thus eliminating the formation of CO2 during the limestone decomposition. An additional advantage of CSS is its high content of valuable vanadium and manganese. The effect of an increase in MgO in slag on its melting point is considered. It has been established that an increase in the proportion of MgO to 14% will not cause difficulties in the processing of blast-furnace smelting products and will reduce the sulfur content in iron and the formation of titanium carbides and carbonitrides.

Improved impurity determination of pure organic substances by differential scanning calorimetry with a dynamic method.

Differential scanning calorimetry can be used to measure the impurity contents of pure organic substances on the principle of freezing-point depression. Impurity determination by differential scanning calorimetry with a dynamic method, which has the advantages of speediness and convenience, remains to be explored. Here, a series of acetanilide and dibenzothiophene samples with various purities was prepared through zone melting, and the samples were then analyzed by gas chromatography-mass spectrometry. A modified dynamic method, including encapsulating the analyte in a volatile pan through cold welding, remelting the analyte with a low heating rate, calculating the melted fraction considering the area of the tailing under the heat-flow curve, and reducing the error from solid-solution formation, is proposed. Encapsulating with a volatile pan using a proper torque gave an accurate result. Remelting gave a lower impurity content and a more narrow and sooth peak of heat-flow compared with the first melting. The impurity-content results calculated by the modified method were usually higher than those calculated by the ASTM standard method. For acetanilide and dibenzothiophene with impurity contents of less than 0.30%, the modified dynamic method showed good accuracy. The proposed method is applicable to determination of reference materials of organic substances with high purity owing to its accuracy and convenience.

Thermal conductivity of solid solutions of Bi2(Te1-xSex )3 (x = 0-0.07)

Relevance. Solid solutions Bi2 (Te1-xSex )3 are effective materials for an n-leg of thermoelectric cooling devices. Recently, concentration anomalies of properties with a low impurity content were detected in these solid solutions (x ~0.01). It is important to establish whether similar anomalies would be observed on the dependence of thermal conductivity λ from the composition of the solid solution, since λ is one of the parameters that determine the thermoelectric quality factor of the material. Purpose. The purpose of this study was to investigate the concentration dependences of the thermal conductivity of the solid solution of Bi2 (Te1-xSex )3 in the interval x = (0-0.07) to identify concentration anomalies and their possible impact on thermoelectric (TE) efficiency. Methodology. Investigation of temperature dependences of thermal conductivity λ was performed by a dynamic calorimeter. Isotherms of λ for different temperatures in the range T = 175-400 K were built on their basis. Results. On isotherms of λ, there is an interval of abnormal growth λ, which becomes more pronounced when the temperature decreases. The presence of this interval is associated with critical phenomena that accompany the transition of the percolation type from dilute to concentrated solid solutions. Conclusions. The estimation of the thermoelectric figure of merit Z of materials is given. It is shown that the detected growth of λ leads to a decrease in Z in the ranges near the critical (x = 0.01), which should be considered in the practical use of solid solutions of Bi2 (Te1-xSex )3

Achieving low-temperature tensile ductility in a swaged W–Y2O3 alloy

The low temperature brittleness of tungsten (W)-based materials has been a long standing problem for their practical applications. In this study, bulk W–Y2O3 alloy rods of 12 mm in diameter were prepared by industrial hydrogen sintering and temperature-controlled rotary swaging. The swaged W–Y2O3 alloy contains a low content of gas impurities (<110 ppm) and exhibits a strong <110> texture in the grain structure. At room temperature, the alloy exhibits pronounced yielding and a certain uniform plastic deformation on tensile loading along the axial direction of the rod, and evident bending ductility as well. The mechanical properties of the swaged W–Y2O3 alloy are superior to the known bulk W-based alloys in the temperature range from room temperature to 200 °C. The excellent room temperature plastic deformation ability of swaged tungsten alloy is originated from its special texture and bimodal grain structure features, which results in grain boundary separation that blocks effectively the cracking on tensile loading along the [110] texture direction.

Design of a multi-configurations divertor for the DTT facility

The standard positive triangularity H-mode tokamak operation with Single Null Divertor (SND) configuration and tungsten monoblocks targets can face some difficulties in providing a solution scalable towards the realization of the fusion reactor. To provide a safer solution, the adoption of alternative divertor magnetic configurations (ADCs) has been considered to provide on the targets a stationary heat load of less than 10 MW/m2 presently considered an upper technological limit for a nuclear fusion reactor and to reduce enough plasma temperature to avoid tungsten sputtering and its possible plasma contamination. Additionally, different plasma scenarios have been considered to avoid the huge transient energy released due to the type-I ELMs of the high confinement H-mode operation. The new high field superconducting divertor tokamak test facility (DTT) [1] is presently under construction to specifically study power exhaust solutions in reactor relevant regimes. The first DTT divertor will use the ITER-like technology based on full tungsten monoblocks bonded on CuCrZr cooling tubes. To test and compare a wide set of different power exhaust solutions, the divertor is being designed to be compatible with the standard single null (SND) configuration but also with some ADCs, like the X divertor (XD) and the hybrid Super-X/long leg SN. Additionally, the l-mode negative triangularity (NT) operation is considered important to explore as a solution to avoid ELMs. Two different closed divertors with the same grazing angle (α = 2°) for the reference SND configuration have been considered: a so called “narrow” one with normalized divertor parameters similar to those presently foreseen for DEMO divertor and the “wide” one with a 50 % wider target aperture which allows testing long legs configurations as well as snowflake divertor configurations (SFD). For the “wide” divertor different dome sizes have been also considered. The comparison between different shapes and their optimization have been done with the 2D edge fluid-kinetic code SOLEDGE2D-EIRENE. The code easily manages all magnetic configurations and can resolve the heat load on all components thanks the mesh filling the whole divertor and vessel volume. In a representative sub-set of all the possible magnetic equilibrium configurations that can be realized in DTT, the edge modelling shows a better performance of the “wide” divertor compared to the “narrow” one. In fact, the “wide” divertor allows to have lower plasma temperature at the targets in pure deuterium at low PSOL power and also lower impurity concentrations is required to achieve plasma detachment by impurity seeding at the reference full power DTT scenario. The results seem to indicate that the improvement due to the longer legs possible with the “wide” divertor can overcome its lower apparent closure compared to the “narrow” divertor solution.

Effect of bias voltage on the structure and properties of CuNiTiNbCr dual-phase high entropy alloy films

The dual-phase structure has been proved to overcome the effect of strength-ductility trade-off of high-entropy alloys. However, most of the high entropy alloy films with larger atomic size difference tend to form a single amorphous structure under non-equilibrium deposition conditions such as magnetron sputtering. In this study, the dual-phase CuNiTiNbCr high entropy alloy film containing the Cu-rich FCC alloy phase and amorphous phase were synthesized by high-power pulsed magnetron sputtering at different bias voltages. The poor affinity of copper with other elements led to the segregation and enrichment of copper to form a Cu-rich FCC phase. The effects of substrate bias voltage on the microstructure, mechanical and corrosion properties of the films were investigated. With the increase of bias voltage, the content of copper in the film decreased, the stress state of the film changed significantly, and the compactness of the structure was improved. The hardness of all films was higher than that of most other high entropy alloy film systems. The films deposited under low bias voltage have better toughness. The film deposited at －50 V showed the best wear resistance due to a combination of high hardness and good toughness. The film deposited at －150 V showed the best corrosion resistance since it had the lowest self-corrosion current density (6.1 ×10−8 A/cm2), which was due to its compact structure and lower impurity content.

Surface-potential-modulated piezoresistive effect of core–shell 3C-SiC nanowires

The effect of surface potential on the carrier mobility and piezoresistance of core–shell silicon carbide nanowires (SiC NWs) was investigated to realize small and sensitive SiC-microelectromechanical systems sensors. The p-type cubic crystalline SiC (3C-SiC) NWs were synthesized via the vapor–liquid–solid method and coated with silicon dioxide (SiO2) or aluminum oxide (Al2O3) dielectric shells to form core–shell structured NWs with different surface potentials. Four-point bending devices (FBDs) with a field-effect transistor (FET) configuration integrating a single core–shell 3C-SiC NW as the FET channel were fabricated to apply an additional electric field and strain to the core–shell 3C-SiC NWs. The fixed oxide charge densities of the SiO2 and Al2O3 shells showed positive and negative values, respectively, which were equivalent to electric fields of the order of several hundred thousand volt per centimeter in absolute values. In the core–shell 3C-SiC NWs with originally low impurity concentrations, the electric field induced by the fixed oxide charge of the shells can determine not only the electrical conduction but also the charge carriers in the NWs. Bending tests using the FBDs showed that the piezoresistive effect of the SiO2-coated NW was almost the same as that of the as-grown 3C-SiC NW reported previously, regardless of the gate voltage, whereas that of the Al2O3-coated NW was considerably enhanced at negative gate voltages. The enhancement of the piezoresistive effect was attributed to the piezo-pinch effect, which was more pronounced in the NW, where the carrier density at the core–shell interface is enhanced by the electric field of the dielectric.

Advances in proteomics sample preparation and enrichment for phosphorylation and glycosylation analysis.

As the common and significant chemical modifications, post-translational modifications (PTMs) play a key role in the functional proteome. Affected by the signal interference, low concentration, and insufficient ionization efficiency of impurities, the direct detection of PTMs by mass spectrometry (MS) still faces many challenges. Therefore, sample preparation and enrichment are an indispensable link before MS analysis of PTMs in proteomics. The rapid development of functionalized materials with diverse morphologies and compositions provides an avenue for sample preparation and enrichment for PTMs analysis. In this review, we summarize recent advances in the application of novel functionalized materials in sample preparation for phosphoproteomes and glycoproteomes analysis. In addition, this review specifically discusses the design and preparation of functionalized materials based on different enrichment mechanisms, and proposes research directions and potential challenges for proteomic PTMs research.

Sustainable extraction of tungsten from the acid digestion product of tungsten concentrate by leaching-solvent extraction together with raffinate recycling

Acid digestion of tungsten concentrates has attracted more and more attention in recent years, sustainable extraction of tungsten from acid digestion product of tungsten concentrates to obtain (NH4)2WO4 solution with low impurity content is the key for ammonium paratungstate production. In this work, a process of extracting tungsten from acid digestion product by leaching-solvent extraction together with raffinate circulation was introduced. The acid digestion product was firstly leached by Na2CO3, and the leaching efficiency was 99.47% with circulation of Na2CO3 solution converted from the raffinate of solvent extraction. The tungsten in pure Na2WO4 solution with 121.26 g/L WO3 could be almost completely extracted by solvents containing 15% N235 or 15% Alamine 308 in one stage. The extraction mechanism of N235 and Alamine 308 was the same, while Alamine 308 showed better performance and higher saturated loading capacities for tungsten extraction. The loaded tungsten was stripped from organic phases using NH3·H2O with stripping efficiency of 99.98%, obtaining (NH4)2WO4 solutions with WO3 concentration above 260 g/L and low impurity content. The raffinate containing high Na2SO4 concentration was converted to Na2CO3 solution by adding BaCO3 and recycled for the leaching of digestion product, which could significantly reduce the discharge of sodium salt wastewater. The presented work provides a cleaner production route for preparing pure (NH4)2WO4 solution from acid digestion product of tungsten concentrates.

Visualization of defects in single-crystal and thin-film PdCoO2 using aberration-corrected scanning transmission electron microscopy

Single-crystal delafossite ${\mathrm{PdCoO}}_{2}$ is known to have an extremely low intrinsic impurity concentration of \ensuremath{\sim}0.001%, demonstrating extraordinarily high conductivity with a mean free path of \ensuremath{\sim}20 \ensuremath{\mu}m at low temperatures. However, when grown as thin films, the resistivity at room temperature increases by a factor of 3--80 times, depending on the film thickness. Using scanning transmission electron microscopy, we identify different classes of defects for the single crystal vs epitaxial thin film. The dominant defect for single-crystal ${\mathrm{PdCoO}}_{2}$ is found to be ribbonlike defects. For the thin films, we identify different types of defects arising in epitaxial thin films mainly due to substrate termination that disrupt the lateral connectivity of the conducting planes. Our results are consistent with the high conductivity of single crystals and increased electrical resistivity of the thin films compared to that of single crystals, suggesting that selecting a proper substrate, improving surface quality, and reducing the step density are the keys to enhance the film quality for utilizing ${\mathrm{PdCoO}}_{2}$ as a platform for future applications.

Phase diagram, thermodynamic studies, and ab-initio calculations of the Ge-Li system

The limiting enthalpy of solution of liquid germanium in the liquid tin ΔsolH¯Ge(l)∞ was measured at 927 K and equals 3.24 ± 0.34 kJ/mol at. The standard enthalpy of formation of intermetallic phases from the Ge-Li system were calculated at 747 K with the use of the solution calorimetric method. These alloys and intermetallic phases were prepared from pure, metallic germanium and lithium, which were melted in a glove-box filled with high purity argon with a very low concentration of impurities. The X-ray diffraction measurements were conducted to verify the structure of the prepared alloys. The electromotive force studies were performed at three temperatures: 634 K, 807 K, and 841 K by the titration technique. Based on obtained results and other thermodynamic quantities available in the literature the thermodynamic properties of phases were optimized, and the Ge-Li phase diagram was determined.