Investigated Composition Range Research Articles

Broadband Dielectric Spectroscopy: Unraveling Na+diffusion and mixed conduction in Na₂O-modified zinc phosphate glasses for electrode material applications

The fundamental understanding of electric charge (ion + polarons/electrons) transport and relaxation mechanism is essential for applications in solid state ionics. In present work, to study Na+ transport, the electrical conductivity of zinc phosphate glasses modified with Na2O has been investigated in temperature range 313K and 473K and frequency range of 100 mHz to 1 MHz. The experimental data of Nyquist plots is fitted with appropriate equivalent circuits at different temperatures which reveals presence of mixed conduction (polaronic + ionic) and Na+ diffusion (at 50 mol% Na2O) in studied glass samples. The values of frequency exponent (s) obtained from the fitting of experimental data of the real part of electrical conductivity with Almond–West equation (WAE) have been used to determine the conduction mechanism. The electric transport in studied glasses occurred via correlated barrier hopping and non-overlapping small polaron tunnelling conduction models depending on the glass composition and temperature range of investigation. Electric Modulus studies further supports the assertion of composition and temperature dependent conduction mechanisms. The activation energies determined from conductivity, electric modulus, and impedance measurements are found to be consistent, indicating a good correlation in the study.

Determination of the indirect bandgap of lattice-matched SiGeSn on Ge

The first experimental results for the indirect bandgap of SiGeSn, lattice-matched on Ge are reported. The necessary condition for lattice-matching on Ge is a constant ratio of Si/Sn = 3.67. Thus, the investigated composition range is cSn={5.0,7.5,10.0}% and precisely investigated using secondary ion mass spectroscopy. The bandgap determination is based on the extraction of the built-in voltage of a SiGeSn pn++ junction utilizing the so-called capacitance-voltage intercept method. Detailed calculations of the band diagram of the pn++ junction to be investigated, including first level approximations for the effective density of states in the valence and conduction band were performed. The results show that the composition of the alloy strongly influences its bandgap and is Eg,SiGeSnL={0.588,0.704,0.413}eV, respectively.

Electrical and optical properties of environmental friendly Li(1‐x)Smx/3NbO3 ceramics for high‐temperature energy storage applications

AbstractThis research article delves into the synthesis and characterization of Li(1‐x)Sm(x/3)NbO3 ceramic, employing a high‐energy ball milling process. The investigation explores the incorporation of Sm3+ at the Li+1 site across a range of compositions (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05). Structural analysis, using x‐ray diffraction (XRD) and Rietveld structural refinement, establishes that within the investigated composition range, no significant changes in the crystal structure are evident. The x‐ray photoelectron spectroscopy revealed the presence of oxygen vacancies as well as the stable oxidation state of different elements like O2−, Nb5+, Sm3+, and Li1+. At sintering temperature 1050°C, the average grain sizes vary approximately from 1.5 to 3.8 μm for different compositions with regular grain morphology. The UV‐Vis analysis reveals a noteworthy reduction in the band gap to 3.09 eV for the x = 0.01 composition. Photoluminescence studies exhibit distinct green, orange, and red bands, with the highest intensity observed for x = 0.01, showcasing promising optical properties. The dielectric permittivity of Sm‐substituted compositions surpasses the response of pure LiNbO3, demonstrating an increasing trend with temperature in the frequency range 100 Hz‐1 MHz intriguingly, no Curie temperature is observed up to 500°C for any composition. The polarization vs electric field hysteresis loop response highlights better polarization characteristics at the room temperature and maximum polarization is 0.66 μC/cm2 for the composition x = 0.05. The energy storage response of the developed compositions is investigated, which reveals a maximum efficiency of 46.64% for x = 0.04 in Li(1‐x)Sm(x/3)NbO3. The tunable optical properties, enhanced dielectric response, and notable energy efficiency of these high TC ceramics suggest their utility across diverse applications. These findings not only contribute to the understanding of functional ceramic materials but also pave the way for their optimized utilization in advanced technological applications, particularly in energy storage devices under nonambient conditions at high temperatures.

Liquid viscosity, interfacial tension, thermal and mutual diffusivities of mixtures of n-eicosane with dissolved carbon dioxide

The thermophysical properties of systems with alkanes with dissolved carbon dioxide (CO2) are of importance in the aspects of carbon capture and storage (CCS), enhanced oil recovery (EOR), Fischer-Tropsch (FT) synthesis, et al. This work continues for our previous studies about the thermophysical properties of several binary systems with alkane and CO2. In this work, the liquid viscosity, interfacial tension, thermal and mutual diffusivity of normal eicosane n-C20H42 with dissolved CO2 were measured with dynamic light scattering (DLS) method from (323 to 473) K and (0.1 to 5.6) MPa. The system's liquid viscosity and interfacial tension were analyzed as a function of pressure under each isotherm line. The polynomial-based empirical correlations were developed for liquid viscosity and interfacial tension with pressure and temperature. The maximum deviations were 4.4 % for liquid viscosity and 1.1 mN·m−1 for interfacial tension. The experimental interfacial tension from the literature was compared with this work, and the deviations were mostly with 0.50 mN·m−1. The mutual diffusivity of the system was nearly a constant along the investigated composition range in this work. The mass diffusion coefficients from the literature agree with this work. The results from this work were expected to provide reliable and accurate fundamental thermophysical properties of liquid with dissolved gas systems in engineering and chemical processes.

Viscosity of slags from joint smelting of oxidized nickel and sulfide copper ores

The work is devoted to the viscosity determination of molten slags from the joint smelting of oxidized nickel and sulfide copper ores. The model slags were synthesized close in composition and structure to real samples, and limiting the investigated composition range (wt.%): iron-containing slag (8.9 CaO, 11.8 MgO, 12.5 Al2O3, 47.4 SiO2, 13.3 FeO, and 5.0 Fe2O3) and iron-free slag formed by removing iron oxides from the iron-containing slag (12.5 CaO, 16.0 MgO, 9.4 Al2O3, and 58.3 SiO2). The experimental (vibrational method) viscosity values for iron-containing (1550−1300 °C) and iron-free (1550−1400 °C) model slags are 0.31−2.33 and 1.28−4.55 Pa·s, respectively. Viscosity estimation by the Kalmanovitch–Frank model shows a discrepancy with the experimental data for iron-containing slag. Regression analysis (by Weimann–Frenkel–Urbain formalism) of the experimental data was carried out, and original empirical models were proposed to predict the primary model slags viscosity in the considered temperature range. Reducing the basicity from 0.7 (iron-containing slag) to 0.6 (iron-free slag) increases viscous flow activation energy from 204 to 236 kJ/mol. To maintain optimal slag viscosity, joint smelting of oxidized nickel and sulfide copper ores should be carried out at a temperature not lower than 1400 °C.

Disentangled structural and vibrational characteristics of methylammonium halide perovskite MAPbBr3-xClx with x = 0 [formula omitted] 3 studied by X-Ray diffraction and Raman scattering

Structural and vibrational characteristics of methylammonium(MA) halide perovskite MAPbBr3-xClx single crystals (x = 0–3) were investigated by using powder X-ray diffraction and Raman scattering experiments. The lattice constant in the cubic phase obtained from powder X-ray diffraction peaks at room temperature showed nearly a linear dependence as a function of composition. On the other hand, some of the Raman mode frequencies obtained from single crystals exhibited substantial changes in both frequency shifts and half widths over the investigated composition range. Especially, the MA torsional mode showed a significant change from 325 to 485 cm−1 and mode splitting as Cl was replaced by Br. This mode splitting was more clearly seen at low temperatures reflecting the symmetry lowering of the local structure. The contrast between the linear change in the lattice constant and the substantial change in the vibrational frequencies and half widths of the MA torsional mode in the intermediate composition range indicates the local heterogeneous environment for the MA cations caused by the substitutional disorder.

Correlations of Composition, Structure, and Hardness in the High-Entropy Alloy System Nb–Mo–Ta–W

Refractory high-entropy alloys are of interest due to the potential of compositionally complex alloys to achieve combinations of mechanical properties such as room-temperature ductility and high-temperature strength rarely found in simpler alloys. To study a large compositional range of the system Nb–Mo–Ta–W, thin-film materials libraries were fabricated by combinatorial sputtering. High-throughput characterization methods were used to systematically determine composition-dependent properties: (I) the extent and stability of the complex solid solution range and (II) the mechanical properties (Young’s modulus, hardness). The whole investigated composition range of Nb20–59Mo9–31Ta10–42W12–32 crystallized in a bcc phase, independent of annealing temperatures ranging from 300 to 900 °C. Mechanical strength values of the Nb–Mo–Ta–W compositions were calculated using the Maresca–Curtin analytical model parameterized with experimental data. A strong positive correlation with measured hardness was observed that allows using this analytical model for optimization of the mechanical strength. We predict that compositions with high Mo contents provide the highest hardness values.

Influence of R2O3 (R=Al, La, Y) on the structure and properties of strontium borosilicate glasses

The influence of R2O3 (R=Al, La, Y) on the structure, thermal, and some physical properties of strontium borosilicate glasses have been investigated by differential thermal analysis, X-ray diffraction, and Fourier-transform infrared spectroscopy. Fourier-transform infrared spectroscopy results showed that the network of the investigated glasses consists mainly of BO3, BO4, and SiO4 structural units. The influence of R2O3 on the properties of strontium borosilicate glasses depends on the structural role of R3+ ions. The experimental results suggest that Al3+ ions act as intermediate in the investigated composition range, while La3+ and Y3+ ions act as modifiers and depolymerize the glass network. The obtained results showed that the glass transition temperature (610–6600С), dilatometric softening temperature (640–6750С), and molar volume (25.03–29.22 cm3/mol) values of the investigated glasses were increased with equimolar substitution of SrO by R2O3. The thermal expansion coefficient (6.8–9.5 ppm/K) of the investigated glasses was found to decrease with increasing the R2O3 content. The obtained results showed that the density (3.03–3.68 g/cm3) values of the investigated glasses were increased with increasing the Y2O3 and La2O3 content and decreased with increasing the Al2O3 content. The tendency to crystallize is higher in glasses containing La2O3 compared to glasses containing Y2O3 or Al2O3. The results obtained in this study indicate that the investigated glasses can be potential candidates for advanced aerospace and electronic applications as heat-resistant electrical insulating glass- and glass-ceramic-to-metal seals and coatings.

A Revision of the Sb-Te Binary Phase Diagram and Crystal Structure of the Modulated γ-Phase Field

A new experimental study of Sb-Te, based on long term annealed samples homogenized by intermediate powdering and re-annealing of the pressed powder pellets was performed. More than 25 samples were prepared, covering the entire composition range between 0 and 60 at.% Te. This part of the phase diagram was disputed for many years, as the number of phases and their crystal structures were uncertain. Samples were characterized by optical microscopy, SEM/EDX, powder XRD and DTA. Our results show the existence of a continuous single phase field (γ) ranging from 11.4 to 56.9 at.% Te at 520 °C. A comparison of all obtained diffraction patterns showed clear evidence for a continuously modulated crystal structure. It was possible to refine all powder patterns by applying a structural model in the (3 + 1)-dimensional super-space group R­3m(0,0,γ). Lattice parameters of the basic cell as well as the modulation vector are varying continuously throughout the phase field and the γq-component ({mathbf{q}} = gamma_{q} cdot {mathbf{c}}^{user2{*}}) of the incommensurate q-vector shows a linear extrapolation to pure Sb (γq = 3/2) and Sb2Te3 (γq = 6/5). In agreement with previous authors, the single-phase field γ was found to have a melting point minimum (30 at.% Te, 535 °C). Furthermore, two peritectic reactions were observed and the course of liquidus lines was determined in the whole investigated composition range. The new phase diagram differs considerably from all previous versions, and, for the first time, gives a complete rationalization of the crystal structures observed in the debated composition area.

Thermodynamic mixing functions of the Fe–Ni–Zr liquid alloys

The mixing enthalpies of liquid Fe–Ni–Zr alloys were studied at 1873 K by means of a high-temperature isoperibolic calorimeter. The study was performed along the section xFe/xNi = 1/1 at xZr = 0–0.45. The limiting partial enthalpy of mixing of undercooled liquid zirconium in liquid Fe50Ni50 (at.%) alloy is (–139 ± 6) kJ⋅mol−1. The integral mixing enthalpy are negative over the investigated composition range. For the integral mixing enthalpy, an analytical expression was obtained by the least square fit of the experimental results and relevant literature data using the Redlich–Kister–Muggianu polynomial. The mixing thermodynamic functions of the Fe–Ni–Zr liquid alloys were modelled in the framework of the associate solution model.

Mechanical Properties of Commercial Purity Aluminum Modified by Zirconium Micro-Additives

The mechanical properties and the fractured surfaces of commercial purity aluminum modified by zirconium micro-additives were investigated by means of experimental examination. A commercial purity Al specimen was used as a reference material and seven Al-Zr alloys in the 0.02–0.14 wt.% Zr composition range (with 0.02 wt.% Zr step) were prepared by microalloying methods. Optical microscopy was used to examine the microstructures and to calculate the grain sizes of the prepared specimens. The phase assemblage diagrams were plotted and the relative amounts of solid phases were calculated at room temperature using FactSage thermochemical software and databases. Proof stress, strength coefficient and strain hardening exponent were measured from the stress-strain curves obtained from tensile experiments and Charpy impact energy was calculated for all specimens. The experiments showed that the grain size of commercial purity Al was reduced by adding any Zr concentration in the investigated composition range, which could be due to the nucleation of new grains at Al3Zr particle sites. Accordingly, the microhardness number, tensile properties and Charpy impact energy were improved, owing to the large grain-boundary areas resulted from the refining effect of Zr, which can limit the movement of dislocations in the refined samples. The basic fracture mode in all specimens was ductile, because Al has an FCC structure and remains ductile even at low temperatures. The ductile fractures took place in a transgranular manner as could be concluded from the fractured surface features, which include voids, ridges and cavitation.

Co-existence of a Cr3+ phase (CaAl2Cr2O7) with hydraulic calcium aluminates at high temperature in the Al2O3–CaO–Cr2O3 system

Obtaining a stable Cr3+ phase at higher temperatures in the presence of hydraulic calcium aluminates (the phases found in calcium aluminate cement, CAC) in the Al2O3–CaO–Cr2O3 system remains a significant challenge in many application areas, as the formation of toxic, carcinogenic, and water-soluble Cr6+ compounds often occur. To address the issue, recently, we synthesized a high-temperature stable Cr3+ ternary compound (CaAl2Cr2O7) with space group P3 (143). In the present work, we investigated the formation-stability of CaAl2Cr2O7 with in-situ calcium aluminate phases at 1500 °C under the CO2 atmosphere in the Al2O3–CaO–Cr2O3 system through solid-oxide reactions route varying Cr2O3 content (at constant Al2O3:CaO ratio). It co-existed with hydraulic calcium aluminates and other phases over the full investigated composition range of 2.76–68.3 mol% Cr2O3 (5–80 wt%). Apart from CAC phases (CaAl2O4, CaAl4O7), major Cr3+-phases are CaAl2Cr2O7 and (Al,Cr)2O3 while (α,β)-CaCr2O4 and Ca(Al,Cr)12O19 formed as minor phases. At a constant Al2O3:CaO ratio of 5.6:4.4 mol% (7:3 wt%), the formation of the CaAl2Cr2O7 phase increases with Cr2O3 content (up to the investigated composition of 26.43 mol%) and then decreases gradually. The solid solubility of Al and Cr in the CaAl2Cr2O7 phase limited over a narrow range, and presumably dependent more on heat treatment condition rather than composition as reflected from the lattice parameter calculations. Though XRD revealed the presence of only Cr3+-phases in the partial CO2 atmosphere, however, traces of Cr6+ could be detected using XPS and leaching tests. However, leachable Cr6+ content (0.095–1.252 mg/L) were much below the United States Environmental Protection Agency (US-EPA) permissible limit of 5 mg/L. The formation mechanism of the CaAl2Cr2O7 and other phases with plausible reactions were also discussed.

Structural and photoelectrochemical properties in the thin film system Cu-Fe-V-O and its ternary subsystems Fe-V-O and Cu-V-O.

Thin-film material libraries in the ternary and quaternary metal oxide systems Fe-V-O, Cu-V-O, and Cu-Fe-V-O were synthesized using combinatorial reactive co-sputtering with subsequent annealing in air. Their compositional, structural, and functional properties were assessed using high-throughput characterization methods. Prior to the investigation of the quaternary system Cu-Fe-V-O, the compositions (Fe61V39)Ox and (Cu52V48)Ox with promising photoactivity were identified from their ternary subsystems Fe-V-O and Cu-V-O, respectively. Two Cu-Fe-V-O material libraries with (Cu29-72Fe4-27V22-57)Ox and (Cu11-55Fe27-73V12-34)Ox composition spread were investigated. Seven mixed ternary and quaternary phase regions were identified: I (α-Cu3FeV6O26/FeVO4), II (Cu5V2O10/FeVO4/α-Cu3Fe4V6O26), III (Cu5V2O10), IV (Cu5V2O10/FeVO4, V (FeVO4/γ-Cu2V2O7/α-Cu3Fe4V6O26), VI (β-Cu2V2O7/α-Cu3Fe4V6O26/FeVO4), and VII (β-Cu3Fe4V6O26/FeVO4). In the investigated composition range, two photoactive regions, (Cu53Fe7V40)Ox and (Cu45Fe21V34)Ox, were identified, exhibiting 103 μA/cm2 and 108 μA/cm2 photocurrent density for the oxygen evolution reaction at 1.63 V vs reversible hydrogen electrode, respectively. The highest photoactive region (Cu45Fe21V34)Ox comprises the dominant α-Cu3Fe4V6O24 phase and minor FeVO4 phase. This photoactive region corresponds to having an indirect bandgap of 1.87 eV and a direct bandgap of 2.58 eV with an incident photon-to-current efficiency of 30% at a wavelength of 310 nm.

Network connectivity and dissolution properties of sodium calcium phosphate glasses

Glasses of xCaO∙(80-x)P2O5·20Na2O system (0 ≤ x ≤ 30% mol %) with constant Na2O content were studied in order to evidence both structural and dissolution properties determined by CaO addition. Transparent vitreous samples were obtained in the investigated composition range. Thermal analysis evidenced the increase of both crystallisation and melting temperatures with CaO content. The relative mass loss of samples in simulated body fluid progressively increased with the extent of P2O5 substitution by CaO. The dissolution properties could be explained in relation with the structural changes concerning the PO4 units connectivity as pointed out by DTA and FTIR analysis.

Determination of accurate interdiffusion coefficients in fcc Ag-In and Ag-Cu-In alloys: A comparative study on the Matano method with distribution function and the numerical inverse method with HitDIC

In this paper, 3 fcc binary Ag-In and 3 fcc ternary Ag-Cu-In diffusion couples were firstly prepared. Based on the measured composition-distance profiles, both the traditional Matano method with distribution functions and the numerical inverse method with HitDIC were then utilized to determine the accurate interdiffusion coefficients in fcc Ag-In alloys at 873 K, 973 K, and 1073 K and Ag-Cu-In alloys at 1073 K. The determined interdiffusivities in fcc Ag-In alloys increases as the composition of In increases. The impurity diffusivities of In in fcc Ag extrapolated from the evaluated interdiffusivities based on the Matano method agree well with the tracer experimental data from the literature. As for fcc Ag-Cu-In alloys, the three-dimensional main interdiffusivities planes at 1073 K were constructed over the investigated composition range. The diffusion rate of In is generally faster than that of Cu. Moreover, the main interdiffusivity of In increases with the increment of both In and Cu concentrations, while the main interdiffusivity of Cu increases with In concentration but decreases with Cu concentration. After that, a comprehensively comparative study on the two methods were performed. The interdiffusivities in both the fcc Ag-In and Ag-Cu-In alloys evaluated from the two methods are consistent with each other, indicating that both methods can result in accurate interdiffusivities in binary and ternary alloys. However, as the number of elements increases, the Matano method becomes inconvenient. While for the numerical inverse method with HitDIC, no such limitation exists, and it can be conveniently applied in alloys with any number of components.

Mechanical characterization and optimization of heat treatment parameters of manganese alloyed austempered ductile iron

Austempered Ductile Iron (ADI) belongs to the family of cast irons whose mechanical properties are altered using austempering heat treatment process. The objective of this paper is to study the effects of heat treatment parameters on manganese alloyed ADI. Hence, austenitization temperature, austempering temperature and austempering time are taken as the control variables along with the manganese content in the material. The effects of heat treatment are studied by measuring the ultimate tensile strength and the hardness of the material. The regression equations are developed to relate the various parameters under study. The microstructures of the specimen reveal that retained austenite content increases with increase in manganese and results in decrease in hardness of the material. The statistical analyses indicate that the austempering temperature is the major factor affecting the variation in hardness and tensile strength with 74.5 % of contribution within the range of values whereas, variation in manganese content does not have significant effect on hardness within the investigated composition range in the material.

Mixing Enthalpies of Liquid Cu–Hf–Ti Alloys Studied by High-Temperature Calorimetry

The partial enthalpies of mixing of titanium and hafnium in liquid Cu–Hf–Ti alloys were investigated at 1873 K along the xCu/xHf = 3 (at xTi = 0–0.25) and xCu/xTi = 3 (at xHf = 0–0.5) sections by a hightemperature isoperibolic calorimeter. The limiting partial enthalpy of mixing of supercooled liquid titanium in liquid Cu–Hf alloy is 2.0 ± 1.5 kJ/mol. The limiting partial enthalpy of mixing of supercooled liquid hafnium in liquid Cu–Ti alloy is –43.0 ± 4.5 kJ/mol. The integral mixing enthalpies of components along the investigated sections are calculated by integrating the Gibbs–Duhem equation. The integral mixing enthalpy is negative in the investigated composition range. The comparison of our experimental results with the calculations according to Miedema’s model shows that this model’s prediction for the ΔmixH function should be treated with caution.

Temperature Dependence of the Pyroelectric Coefficient of AlScN Thin Films

The piezoelectric and pyroelectric properties of aluminum nitride (AlN) can be further enhanced by alloying AlN with scandium nitride (ScN). However, while the pyroelectric effect can strongly affect the performance of electroacoustic devices such as surface acoustic wave (SAW) resonators, the pyroelectric properties of aluminum scandium nitride (AlScN) and their thermal dependence are not well known. In this work, the crystallographic, microstructural, and pyroelectric properties of 900 nm thick pyroelectric Al1−xScxN thin films (x = 0 to 0.3) are investigated. All films have wurtzite‐type crystal structure and are highly c‐axis oriented. The pyroelectric coefficient in the temperature range of 20–80 °C is determined by measuring the generated current as a function of sinusoidal temperature excitation. The effective pyroelectric coefficient of AlScN increases by approximately 85% in the investigated composition range. Moreover, no temperature dependence of the effective pyroelectric coefficient is observed for all samples. The increase of the effective pyroelectric coefficient is explained qualitatively by considering the contribution of primary and secondary pyroelectric effect as well as the substrate clamping.

Poly(lactic acid) (PLA) Based Tear Resistant and Biodegradable Flexible Films by Blown Film Extrusion.

Poly(lactic acid) (PLA) was melt mixed in a laboratory extruder with poly(butylene adipate-co-terephthalate) (PBAT) and poly(butylene succinate) (PBS) in the presence of polypropylene glycol di glycidyl ether (EJ400) that acted as both plasticizer and compatibilizer. The process was then scaled up in a semi-industrial extruder preparing pellets having different content of a nucleating agent (LAK). All of the formulations could be processed by blowing extrusion and the obtained films showed mechanical properties dependent on the LAK content. In particular the tearing strength showed a maximum like trend in the investigated composition range. The films prepared with both kinds of blends showed a tensile strength in the range 12–24 MPa, an elongation at break in the range 150–260% and a significant crystallinity.

Calorimetric investigation of the mixing enthalpy of liquid Co–Cu–Ti alloys at 1873 K

ABSTRACTThe mixing enthalpies of liquid Co−Cu−Ti alloys were investigated at 1873 K using a high-temperature isoperibolic calorimeter. The experiments were performed along sections xCo/xCu = 3/1, 1/3 at xTi = 0 − 0.62 and along section xCo/xCu = 1/1 at xTi = 0 − 0.54. The limiting partial enthalpies of mixing of undercooled liquid titanium in liquid Co−Cu alloys, , are (–128 ± 21) kJ mol–1 (section xCo/xCu = 3/1), (–130 ± 12) kJ mol–1 (section xCo/xCu = 1/1) and (–107 ± 11) kJ mol–1 (section xCo/xCu = 1/3). The integral mixing enthalpies are predominantly negative in the investigated composition range. For the integral mixing enthalpy, an analytical expression was obtained by the least square fit of the experimental results using the Redlich–Kister–Muggianu polynomial.