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Investigation of the structural, optical, elastic and electrical properties of spinel LiZn <sub/>2</sub> Fe <sub/>3</sub> O <sub/>8</sub> nanoparticles annealed at two distinct temperatures
摘要： Nanoparticles of Li0.5ZnFe1.5O4 (LiZn2Fe3O8) with the spinel structure were prepared by a sol–gel auto-combustion method at two different annealing temperatures. X-ray diffractograms and Rietveld refinement confirmed the formation of the spinel structure. The morphology was analyzed by electron microscopy, which showed that the grains were composed of different crystallites. Elastic properties were determined from infrared spectroscopy. It was found that the elastic parameters increased with the increase in annealing temperatures. The band gap depends on the annealing temperature and it decreased on increasing the particle size. The conductivity of the specimen annealed at 500 °C followed either the Jonscher's model or Drude's model depending on the temperature range. This conductivity decreased when the annealing temperature was raised by 600 °C. AC conductivity was found to be controlled by the hopping model. A single relaxation phenomenon was evidenced for each sample from impedance analysis. The Nyquist diagram proved that the samples were simultaneously capacitive and resistive and also supported the presence of multiple relaxation times.
关键词： annealing temperature,spinel,conductivity,LiZn2Fe3O8,impedance analysis,band gap,elastic properties,sol–gel auto-combustion
更新于2025-09-16 10:30:52
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Theoretical investigations on elastic, thermal and lattice dynamic properties of chalcopyrite ZnSnX <sub/>2</sub> (X = P, As, Sb) under pressure and temperature: The first-principles calculation
摘要： We performed the first-principles calculations on the elastic and thermal properties for chalcopyrite ZnSnX2(X=P, As, Sb), employing the ultrasoft pseudo-potentials and generalized gradient approximation (GGA) under the frame of density functional theory. The equilibrium structural lattice constants are in good agreement with reported data. The elastic characteristics were evaluated under high-pressure condition (0–20 GPa), such as the elastic constants, bulk modulus, shear modulus, Poisson’s ratio, Zener anisotropy and compressibility index. Combining with quasi-harmonic Debye model, the thermal properties were confirmed at different temperatures (0–1200 K) and pressures (0–20 GPa), including the heat capacity, thermal expansion, Debye temperature, entropy, and Gr¨uneisen parameter. Based on the semi-empirical relation, the hardness of materials was determined at various temperatures and pressures. Finally, the phonon spectrum curves and vibration frequencies of phonon were evaluated to confirm the thermodynamic stability of ZnSnX2. The Raman scattering spectrum and infrared absorption spectrum were simulated for chalcopyrite ZnSnX2.
关键词： thermal characteristics,lattice dynamic properties,Chalcopyrite,elastic properties
更新于2025-09-10 09:29:36
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First-principles study of elastic, electronic, optical and thermoelectric properties of newly synthesized K2Cu2GeS4 chalcogenide
摘要： In this article, we report the elastic, electronic, optical and thermoelectric properties of recently synthesized K2Cu2GeS4 chalcogenide. The structural parameters are found to be in good agreement with experimental results. The calculated single crystal elastic constants (Cij) show that K2Cu2GeS4 is mechanically stable. The investigated electronic band structures reveal semiconducting characteristics and are consistent with experiment. Important optical constants such as dielectric constants, refractive index, absorption coefficient, photoconductivity, reflectivity and loss function are calculated and discussed in detail. Optical conductivity is found to be in good qualitative agreement with the results of band structure calculations. The Seebeck coefficients for TB-mBJ potential within the studied temperature range vary from ~450 to ~200 m V/K. The anisotropic electrical conductivity and electronic thermal conductivity are observed in the layered structured K2Cu2GeS4. The power factor and electronic thermal conductivity at 800K along xx-axis using TB-mBJ potential are found to be ~6 m Wcm-1K-2 and 0.578 Wm-1K-1, respectively and the corresponding thermoelectric figure of merit is 0.81. The obtained results predict that K2Cu2GeS4 is a promising material in thermoelectric device applications.
关键词： electronic properties,optical properties,elastic properties,thermoelectric properties,K2Cu2GeS4
更新于2025-09-09 09:28:46
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Hardness of polycrystalline SiO <sub/>2</sub> coesite
摘要： We measured elastic moduli and hardness of polycrystalline SiO2 coesite. Translucent polycrystalline bulk coesite with a grain size of about 10 micrometers was fabricated at 8 GPa and 1600°C using a Kawai-type multi-anvil apparatus. The obtained bulk and shear moduli are 94(1) GPa and 60.2(3) GPa, respectively. The resulting Vickers and Knoop hardness values are 10.9(7) GPa and 9.6(4) GPa, respectively, at an indentation load of 4.9 N. Coesite is as hard as other four-fold coordinated silica materials such as quartz and densified silica glasses. The hardness values of coesite and the four-fold coordinated silica materials are about one-third of those of six-fold coordinated silica materials, stishovite and seifertite, which are the hardest known oxides.
关键词： coesite,silicates,mechanical properties,elastic properties,ultrasonic,hardness
更新于2025-09-09 09:28:46
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The structural and elastic properties of InSb1-xBix alloys
摘要： Based on density functional theory, the structural and elastic properties of InSb1-xBix alloys have been studied using first principle calculations. The generalized gradient approximation in the presence of spin-orbit coupling is utilized to perform the calculations presented in this paper. The calculated lattice constants of InSb1-xBix alloys are in good agreement with the available experimental data. The mechanical stability of these alloys is demonstrated using elastic constants. The ductility and brittleness of these alloys are investigated using both Poisson’s ratio and Pugh’s ratio. Moreover, the anisotropy of InSb1-xBix alloys is studied using the universal index and the 3D representation of Young's modulus. According to the obtained values of Poisson’s ratio, the InSb0.5Bi0.5 and InBi alloys are auxetic materials.
关键词： InSb1-xBix alloys,structural properties,Density functional theory,elastic properties
更新于2025-09-04 15:30:14
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Elastic Properties of Fullerites and Diamond-Like Phases
摘要： Diamond-like structures, that include sp2 and sp3 hybridized carbon atoms, are of considerable interest nowadays. In the present work, various carbon auxetic structures are studied by the combination of molecular dynamics (MD) and analytical approach. Two fullerites based on the fullerene C60 and fullerene-like molecule C48 are investigated as well as diamond-like structures based on other fullerene-like molecules (called fulleranes), carbon nanotubes (called tubulanes) and graphene sheets. MD is used to find the equilibrium states of the structures and calculate compliance and stiffness coefficients for stable configurations. Analytical methods are used to calculate the engineering elastic coefficients (Young’s modulus, Poisson’s ratio, shear modulus and bulk modulus), and to study their transformation under rotation of the coordinate system. All the considered structures are partial auxetics with the negative value of Poisson’s ratio for properly chosen tensile directions. It is shown that some of these structures, in a particular tension direction, have a very high Young’s modulus, that is, 1852 GPa for tubulane TA6.
关键词： carbon diamond-like phases,elastic properties,fullerites,molecular dynamics,auxetics
更新于2025-09-04 15:30:14
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Oxyfluoro-zinc-tellurite glasses – Part I: Predicting the elastic properties and glass transition temperature under the substitution of AlF3 by ZnO
摘要： An extensive study has been carried out to predict the elastic properties and glass transition temperature of oxyfluoro-zinc-tellurite (10-x)AlF3-xZnO-90TeO2 (1 ≤ x ≤ 9), (30-x)AlF3-xZnO-70TeO2 (5 ≤ x ≤ 25), (35-x)AlF3-xZnO-65TeO2 (10 ≤ x ≤ 30) and (40-x)AlF3-xZnO-60TeO2 (15 ≤ x ≤ 35) glass systems, for the first time. Changes in the elastic moduli, Poisson’s ratio and glass transition temperature due to the substitution of AlF3 by ZnO have been discussed in terms of molar volume, fractal bond connectivity, packing density and dissociation energy per unit volume of the glass. The correlation between theoretically calculated and experimentally measured elastic moduli and Poisson's ratio has also been studied on the basis of Makishima-Mackenzie’s theory and Rocherulle et al. model. The composition dependence of fractal bond connectivity suggested that the studied oxyfluoro-zinc-tellurite glasses have an intermediate dimensionality between three- and two-dimensional structures. Both AlF3 and ZnO are incorporated into the tellurite network as network modifiers. This results is the conversion of TeO4 trigonal bipyramids into TeO3+1 polyhedral and then to TeO3 trigonal pyramids through breaking of TeeOeTe linkages and creation of non-bridging oxygen atoms. In addition to this, both Makishima-Mackenzie's theory and Rocherulle et al. model appear to be applicable for all the investigated glass systems. The agreement between theoretical and experimental values of elastic moduli and Poisson's ratio is excellent for majority of the samples.
关键词： Rocherulle et al. model,Elastic properties,Makishima–Mackenzie’s theory,Oxyfluorotellurite glasses
更新于2025-09-04 15:30:14