Papers by Keyword: Solid Solution

Abstract: During high-pressure torsion (HPT), the sample positioned between the plungers of the experimental setup is resistant to fracturing, allowing the HPT process to be sustained almost indefinitely. Despite this, relaxation processes taking place within the sample during HPT lead swiftly to the establishment of a steady state. Factors such as hardness, grain size, the scale of second-phase precipitates, electrical conductivity, lattice spacing, among others, rapidly reach a saturation point, albeit after varying revolutions of the plunger. For instance, in the scenario of HPT involving a binary solid solution accompanied by secondary phase particles that act as sources of dissolved atoms, a dynamic equilibrium and competition emerge between the formation and decomposition of a supersaturated solid solution. Consequently, a specific equilibrium state is achieved with a designated concentration (c_ss) of the second component within the solid solution. This equilibrium state is independent of the initial one (referred to as equifinality). The steady-state concentration c_ss can be identified on the solubility limit line (solvus) of the second component in the phase diagram at an effective temperature T_eff. In copper alloys, the value of T_eff grows as the activation enthalpy for the volume diffusion of the second component increases. This amplification signifies a rise in defect concentration and an activation-driven character of mass transfer during HPT.

Abstract: An innovative method of obtaining thin films of semiconductors and other materials, which is based on the differences in components solubility, density, and atomic mass, is developed. Process of producing a thin film of a substance A starts by choosing of another component – substance B that may form a two-component A–B solid solution. Then, it has to be selected third component – substance C that must dissolve substance B well, but A does not. The selection of the composition and conditions of application of the chemical etching process ensure the removal of C and B dissolved in it from the surface of A. The method provides both low- and high-temperature processes. The proposed new principle of obtaining thin films would be attractive due to their reduced size, tunable properties, proper adhesion, preservation of high reliability, possibility of further miniaturization in electronics, and cost reduction.

Abstract: Lead hydroxyapatite (PbHAP, chemical formula Pb₁₀(PO₄)₆(OH)₂) has been synthesized by ceramic (solid-state reaction) and semi-ceramic (precipitation) methods. The samples were prepared through a solid-state reaction conducted at 830 °C for 60 hours, with the y values ranging from 0.95 to 1.00. We have developed and created the most efficient preparation methods. The well-known technique was used - semi-ceramic (precipitation) deposition of lead and hydroxyapatite. For this purpose, several advanced devices were used to obtain an accurate structural structure of lead hydroxyapatite compounds. It has been observed, as in the case of chemical synthesis, that the elements (lead, phosphorus, and oxygen) appear to be distributed homogeneously within the crystals, regardless of the method of composition, which indicates that the samples are homogeneous. More importantly, the "solid-state reaction" method favored a specific composition range, while the "precipitation" method performed well for other composition ranges. The above methods indicate an ideal method, according to the desired structure, that should be developed for lead hydroxyapatite, depending on its composition. This research aims to establish the first steps in developing a new method for preparing lead hydroxyapatite compounds with the desired properties to improve their purity and crystal structure for potential uses in the future.

Abstract: Series of high entropy alloys designed on Hume-Rothery criterion was prepared and the probability of the empirical approach to hydrogen storage materials preparation was investigated. Calculated HEA’s with equimolar compositions were selected from the list of alloys with limited VEC (valence electron concentration), ΔS and ΔH. The phase composition of prepared materials was compared with the prediction model and material characteristics such as chemical composition, and phase composition were studied. In this article material characterization of predicted high-entropy alloys with various prediction parameters values will be presented in terms of empirical prediction methods for solid-state hydrogen storage materials.

Abstract: The X-ray diffraction, microstructure, impedance, electric modulus, and ac-conductivity of Ba(Fe_1/2Ta_1/2)O₃–(Na_1/2Bi_1/2)TiO₃ solid-solutions were studied utilising a traditional high-temperature mixed-oxide technique. The phase-formations of the solid-solutions were determined utilising X-ray data, while SEM micrographs revealed a non-uniform dispersion of grains in the sample of unequal size (~1 – 20 mm). In all of the developed solid-solutions, the frequency (1Hz - 1MHz) dependence of imaginary and real parts of electric impedance in the temperature region of 50 and 500°C showed the NTCR character and hopping type of electrical conduction. The modulus spectrum variation was intrigued by the hopping mechanism for charge transport (temperature-dependent) in the samples with non-Debye type of behaviour. Besides, the low electrical conductivity of these solid-state solutions makes them ideal for industrial applications, particularly as capacitors.

Abstract: The structure, microstructure, Fourier transformed infrared spectra, dielectric, and impact generated energy harvesting characteristics of x(Ba_0.7Ca_0.3)TiO₃–(1-x)Ba (Zr_0.2Ti_0.8)O₃; x = 0, 0.5, and 1.0 synthesized using solid-state reaction method are discussed in this work. The X-ray diffraction (XRD) process was used to examine the forming of a single-phase compound. The Rietveld refinements of XRD data were used in FullProf software to determine crystal symmetry, lattice parameters, and space groups. A scanning electron microscope was taken into use to examine the surface morphology of all of the samples. The samples' phase transition temperature was observed to lie between-10°C and 87°C, shifting toward the higher temperature side as x increased. In the case of x = 0.5, two-phase transitions were discovered at 22°C and 70°C. The value of impact generated output voltage and electrical energy increases as applied mechanical energy increases. The findings of this study point to the possibility of using 0.5(Ba_0.7Ca_0.3)TiO₃–0.5Ba (Zr_0.2Ti_0.8)O₃ ceramic for energy harvesting and sensing purposes.

Abstract: The paper describes the process of obtaining a high-density ceramic material based on magnesium aluminate spinel - material, which feature-wise will be lighter by mass of the used bullet-proof glass, and less resource-proof compared to modern ceramic armored. The sintering was carried out in a vacuum using a modifying gallium oxide additive to intensify the process. The effect of the additive concentration on the phase formation in the magnesium aluminate spinel-oxide gallium system, as well as the density and ceramics light transmission, is considered.

Abstract: The production of a precursor of magnesium aluminate spinel (AMS) by thermic synthesis to obtain a material with high-performance properties is reviewed in the work. The temperature synthesis of AMS is determined, the introduction of the additive is described in the range of concentrations of 3, 5, and 7 mol.%. The current processes during the firing of products have been investigated with a view to the further selection of the firing mode of the ceramic samples, which can be obtained.

Abstract: First, the metallic oxides of PbO, TiO2 and ZrO2 were mixed following (2, 1, 1) molar mass respectively. Then 4 samples were separated (S1, S2, S3 and S4). the first one S1 was subjected to calcination treatments at 600, 700 and 800 °C however, the S2 was treated at 700 °C only, the S3 at 800 °C and S4 at 850 °C. The X ray diffraction of the samples reveals important difference in the phases obtained, at 600 °C the quadratic riche phase of PbTiO3 was mainly observed on sample S1, after the treatment at 700 °C and 800°C, the same XRD patterns were obtained with the same peaks positions and the relative intensity. However the S2 revels different pattern from S1 at 700 °C relative to the formation of the Pb(Zr0.75, Ti0.25)O3 Rhombohedral riche phase. The S3 XRD results reveal also different pattern from S1 at 800 °C relative to the formation of Pb (Zr0.58, Ti0.42) O3 near the Morphotropic phase boundary (MPB) and the S4 confirm these finding. Thin films grown from the S1 and S4 used as target in the RF sputtering system, show important difference in the PZT stoichiometry obtained which is relative to Pb (Zr0.44, Ti0.56) located in the quadratic riche phase and Pb (Zr0.52, Ti0.48) O3 near the MPB respectively.

Abstract: The purpose of the work is influence investigation of modifying Nd₅Mo₃O_16+δ oxygen-conducting fluorite-related compound by lead at the crystal structure and conductivity. The substitution of lead for neodymium was studied by XRD (with structure refinement), scanning electron microscopy, FTIR-spectroscopy and conductivity measurements. The compositions Nd_5-xPb_xMo₃O_16+δ (x = 0 – 1.6) were obtained by a solid state reaction from the oxides. It was determined that single-phase solid solution Nd_5-xPb_xMo₃O_16+δ is formed up to x ≈ 0.82. The Rietveld structure refinement shows that lead is statistically located in the Ln1 and Ln2 positions. The introduction of lead does not significantly affect the nature and values of conductivity.