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Annals of West University of Timisoara - Physics
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ISSN (Print) 1224-9718 - ISSN (Online) 1224-9718
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[370 journals]

Theoretical Prediction of Mechanical Properties of BAlSb Ternary
Semiconducting Alloys
- Abstract: The present work aims to predict the elastic constants and other significant properties of ordered BxAl1-xSb (0 ≤ x ≤ 1) ternary semiconducting alloys. We report the initial results of the elastic stiffness constants, the bulk modulus, the aggregate shear modulus, the Cauchy ratio, the aggregate Young’s modulus, the Born ratio, the isotropy factor, the fracture toughness and the longitudinal, transverse and average sound velocities. The Debye temperature and the melting point were also predicted using two different empirical expressions. Except the Cauchy ratio, which decreases with enhancing boron content x, all other physical quantities of BxAl1-xSb alloys increase gradually and monotonically with increasing of boron concentration x in the range 0-1.Our obtained data for BSb and AlSb binary semiconducting compounds are discussed and analyzed in comparison with experimental and other theoretical values of the literature. Generally, our data for BSb and AlSb are in good agreement with other results reported previously in literature. Indeed, our obtained value (335.82 K) of the Debye temperature for AlSb compound overestimates the result (328.6 K) reported by Salehi et al. by around 2.03%, while that (1520 K) of the melting point for BSb overestimates the result (1500 K) reported recently by Bioud et al. by around 1.34%. Furthermore, to the best of our knowledge, no theoretical or experimental data were reported in the literature on the elastic constants and other properties for BxAl1-xSb alloys to compare with them.
  PubDate: Wed, 27 Apr 2022 00:00:00 GMT
A Comparative Study of Un-Doped ZnO and in Doping ZnO Thin Films with
Various Concentrations, Subjected to Appropriate UHV Treatment and
- Abstract: In this study, we use complementary and sensitive experimental techniques XPS (X-rays Photoelectron Spectroscopy), AES (Auger Electron Spectroscopy, REELS (Reflection Electron Energy-Loss Spectroscopy) and PL (photoluminescence) to investigate and compare the chemical, structure, electronic and optical properties of Un-doped ZnO (UZO) and Indium-doped ZnO (IZO) (4% In; 6% In) thin films. Spray method is used for the growth of these thin films on Si substrate. A treatment process UHV (Ultra-High -Vacuum: Ar+ sputtering followed by checked successive heating until 650°C) is performed. XPS and AES results allow to confirm the clean state of samples and the incorporation of indium into the ZnO matrix to form chemical species of (In-O-Zn) type. The recorded REELS spectra at different primary energies and the PL measurements justify that the UHV treatment plays an important role to improve the physical structure of IZO (6% In).
  PubDate: Sat, 12 Mar 2022 00:00:00 GMT
Ferromagnetic Half-Metal for Spintronic Applications: Ab-Initio
Calculation
- Abstract: The density functional theory (DFT) is used to study the structural, electronic, magnetic properties of Heusler Alloy compounds PdCoMnAl. The calculations are performed via FP-LAPW computational approaches as part of the generalized gradient approximation GGA and modified Becke–Johnson TB-mBJ for exchange-correlation potential. The prediction of the structure of the energy bands and of the densities of states shows a strong hybridization between the states d of the atoms of the transition metals of high valence (Pd) and the states d of the atoms of the transition metal of low valence (Mn) and (Co), which generates a half-metallic gap. In addition, the densities of total and partial states (PDOS) and the results of magnetic spin moments reveal that this compound is stable and ideal half-metallic ferromagnetic. The effects of the unit cell volume on the half-metallic and magnetic properties are crucial. It is interesting to note that our results of the total magnetic moment for PdCoMnAl equal to 5 µB per unit cell, nicely follow the rule µtot = Zt-18.
  PubDate: Wed, 22 Dec 2021 00:00:00 GMT
Spectral Characteristics of Solar Radiation in Timisoara, Romania
- Abstract: This study deals with the spectral distribution of solar radiation in Timisoara, Romania. Solar spectrum at the ground level was estimated based on Leckner’s spectral solar irradiance model and measured atmospheric parameters over the years 2019-2020. The average photon energy index (APE) was used to capture the characteristic signature of the solar radiation spectrum. The results emphasize considerable differences between the solar radiation spectrum in Timisoara and the standard AM1.5G spectrum. During 2019-2020, APE has taken values between 1.841 eV and 1.929 eV, indicating both red- and blue-shift from the standard AM1.5G spectrum. To our best knowledge this is the first study which discusses the signature of solar radiation spectrum in terms of APE for a location in Romania.
  PubDate: Wed, 22 Dec 2021 00:00:00 GMT
Retraction of: Hamada Khelifa, Djaafri Tayeb - Ferromagnetic half-metal
for spintronic applications: Ab-initio calculation. - Annals of West
University of Timisoara, Vol. 63, 2020, No. 1, pp. 14-25 (DOI:
10.2478/awutp-2021-0002).
- PubDate: Wed, 22 Dec 2021 00:00:00 GMT
Investigation of the Temperature on the Thin Layers of Cobalt Oxide
Produced by the Spray Pyrolysis Method Using a Solar Oven
- Abstract: Thin films of cobalt oxide (Co3O4) were prepared on glass substrates by the spray pyrolysis method using a solar concentrator (oven) manufactured in our laboratory. We used different processing temperatures (300° C, 350° C and 400° C). The structural, optical and electrical properties of the different samples were analyzed by X-ray diffraction (XRD), UV-Visible spectroscopy and the Hall effect measurement system. X-ray diffraction observations revealed that cubic crystals are created in all films produced, and the film structure is that of a single phase created with preferential orientation along the (311) axis in films at low temperatures, and the axis (111) for high temperatures. The grain sizes of our products vary between (22.62nm and 66.19nm), depending on the processing temperature. The optical band gap of the crystals obtained was measured. The results of the optical forbidden bands of the crystals obtained, indicated two bands of the values for each element (Eg1 and Eg2). We observed that the values of the effective optical forbidden bands increase by 2.547eV and 3.0731eV with the increase in the production temperature., In addition the film produced experiences a decrease in the Urbach parameters which vary between 162.20meV and 360.81meV depending on the increase in production temperatures. Finally, the films produced have electrical conductivity values of (1.090 [(Ω.cm)−1] to 1.853 [(Ω.cm)−1] and electrical resistivity values of 1.431 (Ω.cm) at 1.853 (Ω.cm), depending on the variation in the production temperature.
  PubDate: Wed, 22 Dec 2021 00:00:00 GMT
Correlation of Rheological Properties of Ferrofluid-Based
Magnetorheological Fluids Using Some Dimensionless Numbers Defined in
Magnetorheology
- Abstract: In this paper we investigated from rheological point of view some samples of ferrofluid-based magnetorheological fluids (FF-MRFs) with different volumic fractions of Fe microparticles, but with the same ferrofluid used as carrier liquid. We correlated the dimensionless flow curves, measured at different values of the magnetic field induction, using either Mason number or Casson number. It has been shown that in this approach, data sets measured under different conditions collapse on a single curve. This master curve is useful for controlling the concentration of Fe particles, so that the magnetic and magnetorheological properties of FF-MRF to be adapted to obtain high-performance applications.
  PubDate: Sat, 20 Nov 2021 00:00:00 GMT
Scattering of Fermions by a Magnetic Dipole Field
- Abstract: In this paper we study the problem of fermions scattering by the field of a magnetic dipole in Minkowski space-time. The amplitude and differential cross section for scattering of massive fermions are obtained using the exact solution of the Dirac equation written in the helicity basis. We found that the most probable transitions are those that scatter the fermions perpendicular to the direction of the magnetic field and we consider only the transverse momenta in our analysis. The differential cross section behavior in terms of scattering angle and energy is graphically analysed and we perform a comparative study with the Coulomb scattering.
  PubDate: Sat, 20 Nov 2021 00:00:00 GMT
Structural, Electronic and Optical Properties of ScGaP Alloys An: Ab
Initio Study
- Abstract: The structural, electronic and optical properties of the of ScxGa1-xP alloys have been investigated by using the full-potential plane-wave FP-LAPW method as implemented in the Wien2k code. The exchange-correlation (XC) energy of electrons was treated using the Perdewe-Burke-Ernzerhof parametrization (PBEGGA), and the Tran-Blaha modified Beck-Johnson potential (TB–mBJ). The lattice constant and the bulk modulus have been calculated and analyzed where a deviation from Végard’s law is observed for both.The calculation of the band structure of binary GaP shows that there is an indirect gap of 2.27 eV, while for the ScxGa1-xP compounds there are direct gaps with values of 1.91 eV, 1, 39 eV, 2.04 eV and 1.849 eV for x = 0.25, 0.5, 0, 75 and 1, respectively.At ambient pressure, the refractive index and the dielectric constant are in good agreement with the experimental results. The extinction coefficient does not begin to increase until a threshold, which represents the optical gap. This threshold is equal to 1.224 eV and it starts to increase to reach a maximum at an energy of 3.551 eV.
  PubDate: Sat, 30 Oct 2021 00:00:00 GMT
Geo-Electrical Method of Assessment of Coefficient of Permeability and
Porosity of Soil of a Poultry Farmland
- Abstract: Leachate collected at the bottom of dead bird’s disposal pits may leak and migrate to pollute groundwater when soils and rocks present are porous. This study assessed the coefficient of permeability (K) and porosity (Ф) of soils and rocks in poultry farmland using 2 Dimensional (2D) electrical resistivity method and soil analysis. Geo-electrical data collection was achieved by using the dipole-dipole array. The field resistivity measurement was carried out along three traverse lines (three Profiles) of 100 m long which were oriented along with East-West directions. These measurements were taken in the order of increasing in offset distance interval of 5 m. The acquired apparent resistivity data were inverted using DIPPROWIN modeling software to perform 2D data inversion. Five soil samples from different locations at depths of 0 – 15 cm and 15 – 30 cm, on the poultry farmland, were collected, transported, and tested in the laboratory. K and Ф were determined using falling head and density methods respectively. The results obtained from the processed field resistivity data from the three profiles were presented as field data pseudo-sections, theoretical pseudo-section, and 2D resistivity structures. The 2D resistivity structure revealed three structures viz; highly conductive, slightly conductive, and resistive. The resistivity values of these structures ranged from 14.1-99.0 Ω m, 100-848 Ω m, and 1350-90330 Ω m respectively. The highly conductive structures were found in profiles 1 and 3 due to the downward migration of the contaminants from the dead bird disposal pit 1 and the feces disposal site through clayey sand soil. This occurs at the depth range of few meters from the surface to greater than 20 m. The presence of the slightly conductive structure is a result of filtration of the contaminants by the soil materials which increased the resistivity of the soil. The movement of the contaminant through the soil is an indication of the porous and permeable nature of the farmland. The resistive structure is only noticeable in profiles 1 and 2 but very prominent at the depth range of 5 m to more than 20 m and 5 m to 35 m along the profile length. The results of the analysis of the five soil samples from the poultry farmland showed a high value of 0.552 and 3.554 x 10−2cm/s of porosity (Ф) and coefficient of permeability (K) respectively. A strong correlation of R2 = 0.9878 existed between Ф and K. With these results geo-electrical method had successfully assessed Ф and K of the soil of the poultry farmland.
  PubDate: Fri, 08 Oct 2021 00:00:00 GMT
Ag Continuous Doped SnO Sensor Selective to Co in Presence of Ethanol at
Room Temperature
- Abstract: This paper contains experimental research to minimize the basic limits of the SnO2 semiconductor oxide gas sensor. The operating temperature is high. In addition, their selectivity diminishes with gasses having the same chemical behavior. An experimental methodology is presented to overcome the difficulties of these metal oxides. The efficiency of the gas sensors made of Ag continuously doped at room temperature is excellent. At the end of the testing processes and security measures supplied, laboratory tests and experiments will be conducted to guarantee the acceptability of the planned study.
  PubDate: Fri, 17 Sep 2021 00:00:00 GMT
First-Principles Calculations of the Structural, Electronic and Optical
Properties of Yttrium-Doped SnO
- Abstract: We use FP-LAPW method to study structural, electronic, and optical properties of the pure and Y-doped SnO2. The results show that by Y doping of SnO2 the band gaps are broadened, and still direct at Γ-point. For pure SnO2 material, the obtained values of the direct band gap are 0.607 eV for GGA-PBE and 2.524 eV for GGATB-mBJ, respectively. This later is in good agreement with the experimental data and other theoretical results. The Fermi level shifts into the valence band and exhibits p-type semiconductor character owing mainly from the orbital 4d-Y. Additionally, the calculated optical properties reveal that all concentrations are characterized by low reflectivity and absorption via wavelength λ (nm) in the visible light and near-infrared (NIR) ranges, which leads to a redshift in the optical transparency.
  PubDate: Mon, 12 Jul 2021 00:00:00 GMT
Structural, Chemical and Optical Properties of Pure and Al-Doped Zno Thin
Films Derived by Sol–Gel Dip Coating Process
- Abstract: Pure and Al-doped ZnO thin films were successfully deposited with sol-gel dip coating on both substrates Si (100) and glass. The structural, chemical, morphological and optical properties as a function of the annealing temperature and dopant atomic concentration were investigated by means of X-ray diffraction, Energy dispersive X-ray, Scanning Electron Microscopy, and spectrophotometry. All the pure and doped films show a polycrystalline nature and hexagonal in structure. Accurate doping was proven by EDX. In addition, the SEM analysis revealed that the films possess uniform distribution throughout the surface and the grain dimension decreases with Al doping. From the transmittance measurements, it is see that all films are over 55% in the visible region and the band gap energy increases from 3.28 to 3.45 eV with the increase of Al concentration.
  PubDate: Mon, 12 Jul 2021 00:00:00 GMT
Determination of the Spread of Heavy Metal from Ori-Ile Battery Waste
Dumpsite Using Electrical Resistivity Method
- Abstract: Contaminants from waste dumpsites have become sources of concern. Disposed wastes (Heavy metal) from battery industries could contaminate soil, agricultural plants, and groundwater. Therefore, this study aimed at the determination of the migration of heavy metal (Lead) from a Battery Waste Dumpsite using the electrical resistivity method. Using Schlumberger array, fifteen (15) Vertical Electrical Soundings (VES) were carried out around a Battery Waste Dumpsite in Ori –Ile, Ikumapaiyi at Olodo community, Ibadan, Oyo State, Nigeria. Preliminary analyses of VES data were performed and were fed into software (WINRESIST 1.0) for qualitative interpretation to reveal apparent resistivity values, the number of layers, and thickness. Three and four layers of topsoil, sandy-clayed, weathered/fractured basement, and basement were obtained. Various values of lowest apparent resistivity and depths of penetration of leached lead on the four sides of the battery waste dumpsite were obtained. The lowest apparent resistivity values obtained were converted to apparent conductivity and plotted against the distance of each VES point. Five collected water samples from available hand-dug wells around the dumpsite were analyzed for the presence of lead using an Atomic Absorption Spectrometer. Graph of apparent conductivity against VES distance indicated a decrease in conductivities with distance, an indication of reduction of Concentration of lead with distance. The level of Lead ranged from 0.081 to 0.770 mg/L which was above the tolerance level of 0.01 mg/L of WHO and SON, an indication of heavy metal pollution in groundwater. This study has established that lead ions were present in groundwater and had spread to a distance of 80 m from the battery waste dumpsite and were more pronounced on the southern region of the dumpsite.
  PubDate: Mon, 12 Jul 2021 00:00:00 GMT
Study of the Structural, Optical, Electrical and Morphological Properties
of Nickel Sulfide Thin Films Used in Supercapacitors
- Abstract: Nickel sulfide (NiS) thin film has been deposited on glass substrates by spray-pyrolysis at 325 ± 5 °C. The precursor aqueous solution was synthetized using hexahydrated nickel nitrates and thiourea. The structural, morphological, optical and electrical properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible spectroscopy and four probes electrical measurements. The XRD analysis confirmed the hexagonal structure of NiS thin film, which was found to crystalize along [010] direction with an average crystallites size of 10.5 nm. The lattice parameters are a = b = 3.420 Å and c = 5.300 Å in the space group P63/mmc. The optical properties of the films were investigated through the transmittance and the reflectance measurements. The results revealed that the material exhibits a direct optical band gap of 1.03 eV. The elementary composition analysis confirmed the presence of Ni and S with a stoichiometry ratio (Ni/S) of 1.05. The morphology analysis revealed a homogenous crack-free, compact appearance and a granular surface in all scanned areas. The average roughness of the surface was 6.48 nm. On the other hand, the film exhibits a high electrical conductivity ca. 1.10 × 105 S/cm at room temperature. The above results show that the prepared NiS in this study has a good crystallization, dense morphology, good stoichiometric ratio and high conductivity; therefore, it stands as a potential candidate for application in supercapacitors as an electrode material.
  PubDate: Fri, 29 Jan 2021 00:00:00 GMT
Diffusion Magnetic Resonance Imaging with Applications to Cardiac Muscle:
Short Review
- Abstract: This review describes in brief recent magnetic resonance imaging (MRI) methods for assessing cardiac structure in healthy and pathologic state using diffusion-weighted (DW) and diffusion tensor imaging (DTI) approaches. A background on the theory and MR pulse sequences employed in DW/DT imaging is given, along with the calculation of diffusion tensor (D), apparent diffusion coefficient (ADC) and fractional anisotropy (FA). Parametric maps derived from DW/DT images can quantify microstructure alterations due to fibrotic collagen deposition, along with associated changes in cardiac muscle anisotropy. Representative examples of ADC and FA parametric maps are shown from ex vivo high-resolution DT images of explanted healthy and scarred hearts obtained from pre-clinical investigations. Furthermore, examples of fiber tractography demonstrating DTI-based 3D (three-dimensional) reconstruction of fiber directions within the heart are illustrated using advanced open-source software. Lastly, future developments and potential translation of DW/DT methods into routine clinical evaluation for cardiac MR imaging protocols are highlighted.
  PubDate: Wed, 16 Dec 2020 00:00:00 GMT
Electro-Magnetic Behavior of Highly Correlated Fluorides KFeF, KCoF and
KNiF: A Comparative Study of Cation Effect
- Abstract: Fluorides-based perovskites are currently the typical materials being used in spintronic devices, optoelectronic and magneto-resistance colossal fields. Solar cells made of Fluoro-perovskite hold much promise for the future of solar energy. The electronic structure and magnetic properties of KFeF3, KCoF3 and KNiF3 Fluorides are studied using ab initio Calculation. We have analysed the structural phases, total and partial electronic densities and band structures within the (DFT) vs the DFT+U description. We show the Electro-Magnetic Behavior using L(S)DA+U vs L(S)DA in a comparative study of cation effect by integrating three types of crystal structures (Cubic (Pm-3m), Four-Layered Hexagonal (P6/mmc), and Orthorhombic (Pnma)). Equilibrium lattices agree very well with experimental and theoretical data. Magnetic moment of each phase is discussed. The obtained results confirmed that the three crystal structures invested here exhibit Ferromagnetic (FM) behavior. The introduction of the Hubbard’s parameter U increases lattice parameters and magnetic moment. We deduce that the second cation plays an important role in the magnetic effects. L(S)DA+U show correctly that KFeF3, KCoF3 and KNiF3 are insulators.
  PubDate: Wed, 16 Dec 2020 00:00:00 GMT
Structural Stability and Magnetic Ordering in BiFeO Perovskite Oxide: A
Comparative Study GGA+U vs L(S)DA+U
- Abstract: Ab initio calculations of BiFeO3 magnetic perovskite are carried. Accurate density functional theory calculations were performed considering a U-Hubbard correction (DFT+U) to account for on-site Coulomb interactions of the 3d-Fe states. We have applied the Full-potential linearized augmented plane waves (FP-LAPW) method. Exchange-correlation effects are treated using the Local Spin Density approximation (L(S)DA+U) vs generalized gradient approximations (GGA+U). Equilibrium lattices agree very well with other theoretical and experimental data. The magnetization energy differences between Spin Up and Spin Dn states are small. Spin effect and magnetic moment obtained from subsequent (L(S)DA+U) and (GGA+U) calculations are also discussed in different magnetic configurations: The Ferromagnetic cubic phase (Pm-3m), The A-type Antiferromagnetic (P4/mmc) and The G-type Antiferromagnetic (Fm-3m). The nature of magnetism arises mainly from the Fe-site exhibiting a G-type antiferromagnetic ordering. The electronic structure shows that BiFeO3 has a metallic band gap. This multiferroic exhibit strong hybridization of the 3d-Fe and 2p-O orbitals. Therefore, the Multiferroic BiFeO3 perovskite has driven significant research interest due to their promising technological potential. It’s a good candidate for potential applications in spintronic, and to aid the development of the next generation of data storage and multi-functional technological devices.
  PubDate: Wed, 16 Dec 2020 00:00:00 GMT
Theoretical Study of the Electronic Properties of XYZ (X = Fe, Co; Y = Zr,
Mo; Z = Ge, Sb) Ternary Heusler: Abinitio Study
- Abstract: In the purpose of exploring new Heusler alloys with different magnetic applications, we have employed first principles calculations method within density functional theory. After checking the structural stability of X2YZ Heusler alloys (X = Fe, Co; Y =Zr, Mo and Z = Ge, Sb), we found that Cu2MnAl type structure is more favorable for most compounds except for X2MoGe and Co2MoSb, were the Hg2CuTi structure is energetically more stable. The trends in magnetic and electronic structures can be predicted by the structure types as well as the different kinds of hybridizations between the constituents. Among the two series only two compounds were identified to be true half metals with potential applications in spintronic devices. While one compound was classified as a nonmagnetic semiconductor with a small band gap. For the rest of materials, we found that the metallic behavior is dominant. These materials show possible interesting features in technical applications as well. The effect of distortion on the magnetic properties of Co2ZrGe and Fe2ZrSb showed that the half metallic character was preserved within a moderate range of volume changes, which makes it possible to grow these materials as thin films with modern techniques.
  PubDate: Wed, 16 Dec 2020 00:00:00 GMT
Optimizing Configurations for Determining the Electromagnetic Properties
of CsFeF, NaFeF, and RbFeF Fluorides: GGA vs GGA+U and TB-mBj Approaches
- Abstract: The structural, electronic and magnetic properties of (Cubic Pm-3m, Hexagonal-4H, orthorhombic Pnma, and orthorhombic Pbnm) phases of AFeF3 Fluorides (A = Cs, Na, and Rb) are reported theoretically using full potential linearized augmented plane waves method within the density functional theory (DFT). Using different exchange–correlation approximations including the generalized gradient approximation (PBE-GGA, WC-GGA, and PBEsol-GGA), also (GGA) with Hubbard potential (GGA + U) and The modified Becke Johnson potential (mBJ), we carried to determine various physical properties. The Calculations revealing that the estimated structural parameters are reliable with the experimentally reported data. Magnetically all these intermetallics are Ferromagnetic (FM). The ground-state energy of different magnetic phases studied showed that the magnetic moments are evaluated per atom, and overestimated by (GGA+U). Transfer charge reveals a strong covalent interaction between Fe-Fe atoms. Their electronic band structure and density of states indicate insulator behavior.
  PubDate: Wed, 16 Dec 2020 00:00:00 GMT