Dependence Of Structural Properties Research Articles

The Study of Temperature Dependent Structural and Elastic Properties of Ni0.5Zn0.5Gd0.05Fe1.95O4 Ferrite Nanoparticles

Published from 1956, the Bulgarian Journal of Physics accepts articles in the fields of: General and Mathematical Physics; Particle Physics and Field Theory; Atomic and Molecular Physics; Nuclear Physics; Fundamental Areas of Phenomenology; Theory of Relativity and Astrophysics; Condensed Matter, Statistical Physics; Cross-Disciplinary Physics; and Related Areas of Science and Technology.

Temperature Dependent Dielectric and Structural Properties of (Ba1-xCax)(Zr0.1Ti0.9)O3, (0.140 ≤ x ≤ 0.160) Ceramics

Ceramic pellets of (Ba1-xCax)(Zr1-yTiy)O3, (x = 0.140 to 0.160, y = 0.9), were prepared via solid- state reaction method followed by double sintering. Dielectric properties (ε, tan δ, and σ) of the prepared compositions were measured, in the temperature range from RT (room temperature) to 450 °C, at various frequencies (12–1000 kHz). The dielectric measurements show a single phase transition, around 100 °C, for the prepared (Ba1-xCax)(Zr1-yTiy)O3 (BCZT) compositions, in the measured temperature range. The structural variation was studied using high temperature X- ray diffraction (HT- XRD) measurements of the compositions with x = 0.150 and 0.155. The HT- XRD results were found consistent with the dielectric measurements, showing structural anomaly at around 100 °C; showing tetragonal phase, between RT and around 100 °C; and cubic phase, above 100 °C, in the measured temperature range.

S vacancies in 2D SnS2 accelerating hydrogen evolution reaction

Precise manipulation of atomic defects is essential for modulating the intrinsic properties of two-dimensional (2D) materials. In this study, sulfur (S) atoms are accurately knocked out in the 2D basal plane of pure tin disulfide (SnS2). By varying the annealing temperatures (250–350°C), SnS2 with different S vacancy concentrations (Vs−SnS2) can be obtained. When SnS2 is annealed at 350°C for 5 h, the S vacancies in the forms of single S atom and double S atoms could reach up to 30.5%. The Vs−SnS2 is tested in the microelectrocatalytic hydrogen evolution reaction (HER). Vs−SnS2 with S vacancies of 30.5% generates superior catalytic performance, with a Tafel slope of 74 mV dec−1 and onset potential of 141 mV. The mechanism has been proposed. First, computation confirms that the absence of S atoms prompts surface charge modulation and enhances electronic conductivity. In addition, the under-coordinated Sn atoms adjacent to S vacancy introduce the lattice distortion and charge density redistribution, which are beneficial to hydrogen binding in HER. In short, accurate knockout of specific atoms by controlling the annealing temperature is a promising strategy to explore structure-dependent properties of various 2D materials.

A comparative study in rocksalt and zincblende structured binary and doped alkaline earth pnictides SrP and SrAs by first-principles perspective

The electronic, magnetic and half-metallic structure-dependent properties of the binary alkaline earth pnictides SrP and SrAs are evaluated using the formalism of density functional theory (DFT) within GGA, GGA + U, and mBJ approaches. The comparison of the volume energy plot shows that the rocksalt structure is the stable structure, while the zincblende structure is the meta-stable structure, whereas the negative cohesive energies predict the stability of the compounds in both structures. The electronic band structure calculations of the binary compounds predicted the exhibition of half-metallic ferromagnetic properties in the zincblende structure and metallic properties in the rocksalt structure. The super-cells are created to dope various transition metal impurities to study changes in electronic and magnetic properties in both structures. The magnetic moments of the half-metallic binary compounds are integer-valued that follow the Slater-Pauling rule of 8-zt. The results showing a pure spin polarization at the Fermi level and the integer-valued magnetic moments suggest that zincblende doped and binary SrP and SrAS exhibit half-metallic ferromagnetism. This kind of material property can be further considered for fabricating spintronics devices.

Copper-Content Dependent Structural and Electrical Properties of CZTS Films Formed by “Green” Colloidal Nanocrystals

Thin films of colloidal CZTS nanocrystals (NCs) synthesized using a “green” approach in water with a variation of the copper-to-tin ratio are investigated by Raman scattering, mid-infrared (molecular vibrations) and near-infrared (free carrier) absorption, X-ray photoemission spectroscopy (XPS), electrical conductivity, and conductive atomic force microscopy (cAFM). We determined the effect of the actual Cu content on the phonon spectra, electrical conductivity, and spectral parameters of the plasmon band. An increase in the electrical conductivity of the NC films upon annealing at 220 °C is explained by three factors: formation of a CuxS nanophase at the CZTS NC surface, partial removal of ligands, and improved structural perfection. The presence of the CuxS phase is concluded to be the determinant factor for the CZTS NC film conductivity. CuxS can be reliably detected based on the analysis of the modified Auger parameter of copper, derived from XPS data and corroborated by Raman spectroscopy data. Partial removal of the ligand is concluded from the agreement of the core-level XPS and vibrational IR spectra. The degree of lattice perfection can be conveniently assessed from the Raman data as well. Further important information derived from a combination of photoelectron and optical data is the work function, ionization potential, and electron affinity of the NC films.

Crystal Structure Control of Binary and Ternary Solid-Solution Alloy Nanoparticles with a Face-Centered Cubic or Hexagonal Close-Packed Phase.

The crystal structure significantly affects the physical and chemical properties of solids. However, the crystal structure-dependent properties of alloys are rarely studied because controlling the crystal structure of an alloy at the same composition is extremely difficult. Here, for the first time, we successfully demonstrate the synthesis of binary Ru-Pt (Ru/Pt = 7:3) and Ru-Ir (Ru/Ir = 7:3) and ternary Ru-Ir-Pt (Ru/Ir/Pt = 7:1.5:1.5) solid-solution alloy nanoparticles (NPs) with well-controlled hexagonal close-packed (hcp) and face-centered cubic (fcc) phases, through the chemical reduction method. The crystal structure control is realized by precisely tunning the reduction speeds of the metal precursors. The effect of the crystal structure on the catalytic performance of solid-solution alloy NPs is systematically investigated. Impressively, all the hcp alloy NPs show superior electrocatalytic activities for the hydrogen evolution reaction in alkaline solution compared with the fcc alloy NPs. In particular, hcp-RuIrPt exhibits extremely high intrinsic (mass) activity, which is 3.1 (3.2) and 6.7 (6.9) times enhanced compared to that of fcc-RuIrPt and commercial Pt/C.

Sintering Mechanism and Enhanced Piezoelectric and Crystal Structural Properties of (1-x)Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 Lead Free Ceramics

A lead-free piezoelectric ceramic, (1-x)Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 (hereafter (1-x)BZT-xBCT), was investigated for functional device applications. Lead-free piezoelectric materials with high piezoelectric charge coefficients and voltage coefficients are indispensable for functional industrial applications. Piezoelectric ceramic specimens tend to shrink in size during the sintering process without melting. This study focused on this phenomenon as a unique characteristic of piezoelectric ceramic materials, and derived the materials’ activation energies from this phenomenon, employing the Arrhenius relationship. Then the estimated activation energy was employed to determine the relationship between the piezoelectric properties and crystalline properties, while varying sintering temperature and chemical stoichiometric composition. Piezoelectric properties can change depending on the sintering temperature and process conditions. Crystalline properties and piezoelectric properties can be influenced by the sintering temperature and holding times. In this research, sintering temperature dependent structural and dielectric properties were investigated. (1-x)BZT-xBCT ceramics showed the highest piezoelectric coefficient of 470 pC/N. Sintering temperature dependent shrinkage rate and activation energy were estimated and calculated for the various sintering processes. In this research, two different activation energies for the shrinkage process were estimated.

Composition dependent phase structure, dielectric and electrostrain properties in (Sr0.7Bi0.2□0.1)TiO3–PbTiO3–Bi(Mg0.5Ti0.5)O3 systems

Composition dependent transitions from normal ferroelectrics to nonergodic and finally to ergodic relaxor phase are observed in 0.7(Sr0.7Bi0.2□0.1)TiO3–(0.3 − x)PbTiO3–xBi(Mg0.5Ti0.5)O3 system (SBT–PT–xBMT, □ represents A–site vacancy). Rietveld refinement results show that with increasing BMT content, the system experiences a gradual transition from coexistence of pseudocubic and tetragonal (P c + T) to P c phase. The ferroelectric–relaxor phase transition and freezing temperature gradually decreases with addition of BMT content accompanied by an enhanced relaxor degree, which produces local disorder and polar nanodomains. This is also verified by Raman spectra and piezoelectric force microscopic analysis. The P–E loops transform from square to slant and finally to slim shape with increasing BMT component and an electric field-induced strain of ∼0.21% with ultralow hysteresis of ∼3.7% is obtained for x = 0.04 composition. The underlying mechanism for the large strain with low hysteresis lies in the existence of nonergodic and ergodic relaxor phase boundary and polar nanodomains at room temperature. Additionally, the multiphase coexistence contributes to a flatten free energy profile and thus contributing to such superior performances, as explained by a modified phenomenological model. High electrostrain with ultralow hysteresis in SBT–PT–xBMT systems are promising candidates in high–precision actuator applications.

In Silico Prediction of Food Properties: A Multiscale Perspective

Several open software packages have popularized modeling and simulation strategies at the food product scale. Food processing and key digestion steps can be described in 3D using the principles of continuum mechanics. However, compared to other branches of engineering, the necessary transport, mechanical, chemical, and thermodynamic properties have been insufficiently tabulated and documented. Natural variability, accented by food evolution during processing and deconstruction, requires considering composition and structure-dependent properties. This review presents practical approaches where the premises for modeling and simulation start at a so-called “microscopic” scale where constituents or phase properties are known. The concept of microscopic or ground scale is shown to be very flexible from atoms to cellular structures. Zooming in on spatial details tends to increase the overall cost of simulations and the integration over food regions or time scales. The independence of scales facilitates the reuse of calculations and makes multiscale modeling capable of meeting food manufacturing needs. On one hand, new image-modeling strategies without equations or meshes are emerging. On the other hand, complex notions such as compositional effects, multiphase organization, and non-equilibrium thermodynamics are naturally incorporated in models without linearization or simplifications. Multiscale method’s applicability to hierarchically predict food properties is discussed with comprehensive examples relevant to food science, engineering and packaging. Entropy-driven properties such as transport and sorption are emphasized to illustrate how microscopic details bring new degrees of freedom to explore food-specific concepts such as safety, bioavailability, shelf-life and food formulation. Routes for performing spatial and temporal homogenization with and without chemical details are developed. Creating a community sharing computational codes, force fields, and generic food structures is the next step and should be encouraged. This paper provides a framework for the transfer of results from other fields and the development of methods specific to the food domain.

Temperature-dependent structure and electromechanical properties of Er doped PMN-PT single crystal grown by modified Bridgman technique

In this work, the Er-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal with a large size was successfully grown by the modified Bridgman technique. The temperature dependent phase structure, domain configuration and electromechanical properties of the single crystal with the composition of 2 wt%Er-0.66PMN-0.34PT (Er-0.66PMN-0.34PT) were investigated in detail. For [001]C oriented Er-0.66PMN-0.34PT single crystal, it is found that the room temperature phase structure is the coexistence of rhombohedral (R) and monoclinic (M) phases and M phase is dominated. The piezoelectric constant d33 through the converse piezoelectric effect is about 2410 pC/N. The phase transition from R+M to tetragonal (T) phase begins at 80 ℃ and finishes at 120 ℃. Between 80 ℃ and 120 ℃, the single crystal belongs to the coexistence of R, M and T phases. At 135 ℃, the T phase and polar nanoregions (PNRs) transform into cubic phase and PNRs. The compliance constantss33Dand s33E, longitudinal coupling factor k33 and piezoelectric constant d33 increase by 32%, 77%, 34% and 133%, respectively, with temperature increasing from 22 ℃ to 80 ℃. The ultrahigh increase of d33 is derived from the increase of dielectric constant due to easier polarization rotation and domain wall movement at elevated temperature. Our results will helpful for the study of rare-earth doped relaxor ferroelectric single crystals.

Structural, microstructural and temperature dependent magnetic properties of Mg–Ni doped CoCr2O4 ceramics

In the present work, [Co(1-(x + y)) MgxNiy][Cr2]O4 (CMNCr)(where, x = y = 0, 0.10, 0.20) NPs are examine in detail by using experimental results. Solution combustion method is adopted to prepare the CMNCr NPs. Experimental results were studied to understand structure (using XRD), microstructure (using SEM) and magnetic behaviour (using SQUID). The structural analysis was confirmed a single-phase spinel cubic structure with singular structural distortions associated with Mg–Ni doping and the generation of metal vacancies. SEM micrographs of all samples reveal their highly porous nature. EDS was utilized to examine the elemental analysis of the samples. The formation of spinel cubic structure without impurity were also confirmed by Fourier-transform infrared (FTIR) spectroscopy and the same tool is used to investigate the absorption bands related to the A-site and B-site. For all samples, paramagnetic phase to ferrimagnetic phase transition observed at TC and conical spiral spin order transition observed at TS. The curie temperature is found to be 98 K, 89 K, and 85 K for [Co][Cr2]O4, [Co0.8 Mg0.1Ni0.1][Cr2]O4 and [Co0.6 Mg0.2Ni0.2][Cr2]O4 samples, respectively. The spiral transition temperature is found to be 26 K, 14 K and 8 K for [Co][Cr2]O4, [Co0.8 Mg0.1Ni0.1][Cr2]O4 and [Co0.6 Mg0.2Ni0.2][Cr2]O4 samples, respectively. All of the samples exhibit paramagnetic behaviour above TC. The negative magnetization effect were observed in [Co0.6 Mg0.2Ni0.2][Cr2]O4 NPs. 20% of Mg and 20% of Ni substitution to Co site in [Co][Cr2]O4 leads to the evident magnetization reversal at the compensation temperature with an applied magnetic field of 100 Oe. The M − H loop at 10 K exhibits large coercivity due to the spiral spin ordering. This phenomenon of negative magnetization in the material results in a stable state of magnetization in the material, which has significant applications in the field of magnetic storage devices.

Structural and frequency dependent dielectric properties of Ba doped Ni–Zn ferrite powders

In this work, Ba doped Ni–Zn ferrite (Ni0.8-xBaxZn0.20Fe2O4 (x = 0.1, 0.5, and 0.7) were prepared by sol-gel method. The X-ray diffraction pattern confirmed the structure of the samples to be cubic spinel structure with Fd3m space group. The average crystallite size and lattice parameters were found to increase with increase in Ba doping concentration. Fourier transform infrared spectroscopy ascertained the spinel structure by displaying the characteristic absorbance bands for the Ba doped Ni–Zn ferrite. Enhanced dielectric constant and reduced dielectric loss were obtained. The electronic conducting property of the ferrites were studied using impedance spectroscopy. The Cole–Cole plots were helpful in bringing out the non-Debye relaxation prevalent in the doped samples. These Ba doped Ni–Zn ferrites are expected to be potential candidates in high frequency electronic applications and magnetic memory devices.

First-principles prediction of pressure dependent mechanical, electronic, optical, and superconducting state properties of NaC6: A potential high-Tc superconductor

Very recently carbon-rich NaC6 with sodalite-like structure has been predicted to show high superconducting transition temperature above 100 K at relatively low applied (compared to high-Tc hydrides) hydrostatic pressures. We have investigated the pressure dependent structural, elastic, electronic, superconducting state, and optoelectronic properties of NaC6in this study. Some important thermophysical properties have also been explored. The elastic properties along with Poisson’s and Pugh’s ratios and optoelectronic parameters are investigated for the first time. NaC6 was found to be structurally stable only at high pressures at and above 40 GPa, in agreement with previous study. The compound is highly ductile and the chemical bonding is prominently metallic in nature. The Debye temperature shows strong pressure dependence. The Grüneisen parameter also exhibits significant pressure dependence. The electronic band structure reveals metallic character and consists of highly dispersive and almost flat bands crossing the Fermi level. Both the electronic density of states at the Fermi level and repulsive Coulomb pseudopotential increase gradually with increasing pressure in the range 40 GPa to 70 GPa. The degree of dispersion in the E(k) curves depend weakly on pressure both in the valence and conduction bands. The optical parameters spectra, studied for the first time, correspond well with the electronic band structure. NaC6 absorbs and reflects electromagnetic radiation quite efficiently in the mid-ultraviolet region. Superconducting transition temperatures of NaC6 have been estimated at different pressures and compared with previously reported values. The effects of various parameters on Tc have been discussed in details.

First principles study on thickness dependent structural and electronic properties unveiling the growth and stability of 2D layered II-VI semiconducting compounds.

By employing first principles density functional theory calculations on thickness dependent structural and electronic properties of (0001) surface slabs of wurtzite MX compounds, our study demonstrated the possibility of the existence of 2D layered materials from II-VI group traditional semiconducting compounds that are widely used in various fields. Our calculations revealed that (0001) surface slabs of wurtzite ZnO and CdO compounds prefer to stabilize as sp2 hybridized - atomically thin graphitic layers as observed in earlier work, which are separated by van der Waals distances, when compared to the respective wurtzite slabs. On the other hand, for surface slabs of other ZnX and CdX (X = S, Se, Te) compounds, sp3 hybridized bilayers, which comprise an X-Zn(Cd)-Zn(Cd)-X structural arrangement, are energetically stable until certain thicknesses of the slabs. Both 2D layered MO and MX systems are electronically insulating in nature. When increasing the number of layers in these systems, the band gap decreases due to the widening of the energy bands. Our calculations further confirmed that all of these 2D systems possess structural, elastic, and lattice dynamical stabilities, depicting their compatibility in optoelectronics and photovoltaic applications, as confirmed by their effective mass and mobility.

Thickness dependent structural and magnetic properties investigation of Co film interfaced with Hf

Thickness dependent structural and magnetic properties of Co films interfaced with Hf have been studied. X-ray reflectivity (XRR) and Grazing Incidence X-ray Diffraction (GIXRD) provides the structural properties of as-deposited samples. Film thicknesses as observed from XRR analysis are further implemented to study the magnetic properties of samples as function of Co film thickness, using magneto optical Kerr effect (MOKE) and polarized neutron reflectivity (PNR). MOKE results show the variation of magnetic coercivity with Co film thickness which exhibits a maximum value around 6 nm. Effective magnetic moment of samples as obtained from PNR fitting displays a linear variation with film thickness. Extrapolation of such variation on thickness axis show presence of magnetically dead layer (MDL) at interface, of thickness below 1 nm, in agreement with the reported values in literature for magnetic films interfaced with 5d heavy metals.

Investigation of the Structural and Temperature Dependent Electrical Properties of Mzno (M = CE and Sm) Schottky Diode Devices Fabricated Using the Sol-Gel Spin Coating Technique

Investigation of the Structural and Temperature Dependent Electrical Properties of Mzno (M = CE and Sm) Schottky Diode Devices Fabricated Using the Sol-Gel Spin Coating Technique

Architectural design of core-shell nanotube systems based on aluminosilicate clay.

A nanoarchitectural approach to the design of functional nanomaterials based on natural aluminosilicate nanotubes and their catalysis, and practical applications are described in this paper. We focused on the buildup of hybrid core–shell systems with metallic or organic molecules encased in aluminosilicate walls, and nanotube templates for structured silica and zeolite preparation. The basis for such an architectural design is a unique Al2O3/SiO2 dual chemistry of 50 nm diameter halloysite tubes. Their structure and site dependent properties are well combined with biocompatibility, environmental safety, and abundant availability, which makes the described functional systems scalable for industrial applications. In these organic/ceramic hetero systems, we outline drug, dye and chemical inhibitor loading inside the clay nanotubes, accomplished with their silane or amphiphile molecule surface modifications. For metal–ceramic tubule composites, we detailed the encapsulation of 2–5 nm Au, Ru, Pt, and Ag particles, Ni and Co oxides, NiMo, and quantum dots of CdZn sulfides into the lumens or their attachment at the outside surface. These metal–clay core–shell nanosystems show high catalytic efficiency with increased mechanical and temperature stabilities. The combination of halloysite nanotubes with mesoporous MCM-41 silica allowed for a synergetic enhancement of catalysis properties. Finally, we outlined the clay nanotubes’ self-assembly into organized arrays with orientation and ordering similar to nematic liquid crystals, and these systems are applicable for life-related applications, such as petroleum spill bioremediation, antimicrobial protection, wound healing, and human hair coloring.

Strain dependent structural and electronic properties of two-dimensional janus In2SeTe monolayer

In the present work, the structural and electronic properties of Indium base two dimensional Janus In2SeTe monolayer have been studied by using first principle calculations based on density functional theory. The optimisation of the Janus monolayer system is done by applying a vacuum in the z-direction. The optimised lattice constant is around 4.23 Å. The janus monolayer shows honeycomb lattice structure from the top side view. The band structure of In2SeTe janus monolayer is calculated by using generalized gradient approximation (GGA). We have calculated the total density of state (TDOS) and projected density of state (PDOS) for the janus monolayer. The bi-axial strain is applied and its effects are studied. From the study, it is found that In2SeTe has a potential application in electronics and optoelectronic.

Bandgap tuning with pressure for plausible piezoelectric and electronic applications of Lanthanum oxides LaMO3 (M = Al, Ga, Ti and V)

In this article, we have used density functional theory to investigate the pressure dependent structural, elastic, thermal and electronic properties of LaMO3 (M = Al, Ga, Ti and V) compounds. Optimized structural attributes suggest all compounds are thermodynamically stable based on enthalpy of formation, ground state optimizations and tolerance factor. Moreover, elastic stability criteria also portray results in support of the structural stability of compounds. In electronic properties, the density of states plot suggests anti-ferromagnetic attributes. While transition in the band gap from indirect to direct is observed at 50 GPa for all studied compounds except for LaGaO3. In mechanical properties, stiffness, super-plasticity and moduli of elasticity of the studied compounds observed to increase linearly with pressure. The compound LaTiO3 has shown plausible piezoelectricity under pressure. We expect that studied compounds will fulfil requirements of high pressure optoelectronic sensors and devices.

Surface modeling of photocatalytic materials for water splitting.

The photocatalyst surface is central to photocatalytic reactions. However, it has been a challenge to explicitly understand both the surface configuration and the structure-dependent photocatalytic properties at the atomic level. First-principles density functional theory (DFT) calculations provide a versatile method that makes up for the lack of experimental surface studies. In DFT calculations, the initial surface model greatly affects the accuracy of the calculation results. Consequently, establishing a more realistic and more reliable material surface models is undoubtedly the first step and the most important link in theoretical calculations. The aim of this Perspective is to provide a general understanding of the methods for the surface modeling of photocatalytic materials in recent years. We begin with a discussion of the basic theories applied in photocatalytic surface research, followed by an explanation of the importance of surface modeling in photocatalysis. We then elaborate on the advantages and disadvantages of the basic surface model and briefly describe the latest surface modeling methods. Finally, we evaluate the rationality of current surface modeling methods. We summarize this Perspective by prospecting the developing directions of photocatalytic surface research in the future. It is believed that a reasonable surface model should be verified by both experimental characterization and theoretical computation with negative feedback.