Manopradha N.Gowri S.Rama S.Selvaraju K....
5页查看更多>>摘要：? 2021 Elsevier B.V.The single crystals of pyridine-2-carboxylictrichloroacetate (P2CT) were synthesized using standard method at room temperature. Nucleation parameters such as, radius of critical nucleus, nucleation rate, and interfacial and volume free energy has been estimated. The solubility of the crystal at different temperatures is analyzed. Thermodynamic parameters from vibration analysis are compared with the enthalpy obtained from solubility to predict the stability of the crystal. X-ray diffraction investigating the structural aspects establishes the crystal structure belonging to crystal system as monoclinic nature. Williamson–Hall approach assesses the structural characteristics of the grown crystal: average crystallite size along with lattice strain. In between 220 and 1000 nm wavelength range, the optical absorption spectra of P2CT are recorded. Based on derivation of absorption spectrum fitting method, optical energy band gap and nature of optical transitions in the crystal is determined. Vickers microhardness test estimates the hardness parameters and elastic stiffness is evaluated through Wooster's empirical relation.
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NSTL
Elsevier
Hcini F.Zemni S.Hcini S.Wederni M.A....
5页查看更多>>摘要：? 2021 Elsevier B.V.In this work, the structural, optical, and dielectric properties for Mg0·6Cu0·2Ni0·2Cr2O4 chromite sample prepared by sol-gel process were investigated. The XRD characterization for this sample confirmed the development of the face-centered cubic spinel structure with Fd3￣m space group. From the UV–Vis optical absorbance, the synthesized chromite shows significantly lower direct band gap energy and has an appropriate absorption rate in the visible light region. The variations of penetration depth, extinction coefficient, refractive coefficient, dispersion energy parameters, and dielectric permittivity constants were also interpreted. The Non-Overlapping Small Polaron Tunneling (NSPT) and the Correlated Barrier Hopping (CBH) are the suitable models to describe the conduction process for the prepared sample. The behavior of dielectric constants has been interpreted based on the Maxwell-Wagner's theory of interfacial polarization. The behavior of imaginary part of impedance (Z″) shows a dielectric-relaxation phenomenon in the sample with activation energies near to those determined from the conductivity study.
原文链接:- NSTL
- Elsevier
Chandra S.Chandra Shekar N.V.Kalavathi S.Shwetha G....
5页查看更多>>摘要：? 2021 Elsevier B.V.First principles calculations on Sc2CrB6 crystal revealed the existence of Dirac Cone in its electronic structure for the first time. The compound has an interesting crystal structure with 2D boron layers with hexagonal, pentagonal, heptagonal boron rings sandwiched between the metal layers. Calculations show that the compound has a mixed covalent and metallic nature of the bonding. Also, ground state ferromagnetic behaviour is predicted for the metallic bonded Sc2CrB6. Here the magnetization arises mostly from the Cr atom with enhanced contribution from the remaining elements. Interestingly, band crossing is seen at the Fermi level with spin polarization indicating the existence of Dirac cone in Sc2CrB6. Apart from this, high-pressure calculations up to about 67 GPa reveal a pressure-induced transition from ferromagnetic state to non-magnetic state around 30.3 GPa.
原文链接:- NSTL
- Elsevier
Jiang X.Guo Z.Li X.Tao C....
5页查看更多>>摘要：? 2021 Elsevier B.V.Large-sized multiferroics Pb(Fe1/2Nb1/2)O3 (PFN) single crystal was grown by Bridgeman method in order to understand the giant dielectric response by investigating the electrical conductivity and dielectric properties. The synchrotron radiation soft x-ray absorption spectrum revealed the valence states of Fe in PFN crystal. PFN exhibits semiconductor behaviors in the thermal active electrical conductivity investigation. Besides, the frequency-dependent dielectric constants were measured in the frequency range from 100 Hz to 1 MHz to study the dielectric relaxation behaviors. Two relaxation processes were found and described by Havriliak-Negami equation. The origin of dielectric relaxation in PFN with semiconductor characters was discussed based on the universal relaxation law for a dipolar system.
原文链接:- NSTL
- Elsevier
Wang J.Bao L.Tegus O.Chao L.M....
5页查看更多>>摘要：? 2021 Elsevier B.V.Nanocrystalline Eu-doped PrB6 ultrafine powders have been successfully fabricated through solid-state chemical reaction of Eu2O3, PrCl3 and NaBH4 as raw materials. The optical absorption properties of the synthesized samples were investigated by experimental measurement and theoretical calculation. As a result, a strong red-shift of transmittance wavelength of nanocrystalline PrB6 is achieved via altering the Eu doping. Theoretically, the doping of divalent Eu into trivalent PrB6 reduces the plasma frequency excitation energy and increases the corresponding transmittance wavelength. Additionally, the synchrotron radiation absorption shows that Pr and Eu atoms exist in the form of Pr3+ in PrB6 and Eu2+ in EuB6, and X-ray photoelectron spectroscopy results also indicate that Eu exists in the state of Eu2+ in the nanocrystalline Pr0.4Eu0.6B6, which confirms that the Eu doping reduces the number of conduction electrons in PrB6 and decreases the plasma frequency excitation energy.
原文链接:- NSTL
- Elsevier
Ristic Z.AnticDramicanin M.D.Ciric A....
5页查看更多>>摘要：? 2021 Elsevier B.V.Two experimental practices in luminescence intensity ratio (LIR) thermometry based on the spectral deconvolution (SD) and separation at chosen wavelength (WS) were analyzed for the case when sharp emission is overlapping with a broad one, which is frequently the case for Cr3+ and Mn4+ in the intermediate or strong crystal fields. Their performances were compared showing that, depending on several parameters, separation at chosen wavelength method gives lower sensitivities than spectral deconvolution one. With requirement that the sharp emission quenches at high temperatures, which is also the case for the mentioned luminescent centers, an alternative method, named approximate deconvolution (AD) is proposed. The novel method retains the simplicity of the WS, while matching the sensitivities of the SD method. The detailed algorithm for the AD method is presented. Although the temperature resolution is not improved, the AD method allows fit to the Boltzmann equation and extraction of the physically relevant parameters. All three methods are compared using Cr3+ emission in LiAl5O8, MgAl2O4 and YAG showing that WS gives significantly lower sensitivities than SD and AD, while SD and AD are highly matching in performance.
原文链接:- NSTL
- Elsevier
Naz G.Shabbir M.Ramzan M.Haq B.U....
5页查看更多>>摘要：? 2021 Elsevier B.V.Metal-doped zinc oxide nanostructures (ZONSs) of schemes CuxZn1?xO and MgxZn1?xO (x = 0, 0.01, 0.1 and 0.5 M) were synthesized via co-precipitation technique. The structural parameters of as-prepared ZONSs were investigated from XRD technique and doping concentration limit for both types of dopant was found, causing a shift in the Eg value based on the availability of density of states for that dopant. SEM analysis confirmed thin sheet-like nanocrystalline morphologies of all samples within size range 78–450 nm. Optical analysis revealed that higher concentration of Cu in the sample resulted in overlapped impurity states following a considerable increase in its Eg value. Among all samples, Cu0.1 and Mg0.01 samples with reduced PL emission, exhibited maximum degradation of MB dye under direct-sunlight exposure of few seconds. As positively charged metal-doped ZONSs attract more toward Gram-negative bacterial membrane, the suggested samples have shown improved antibacterial performance against Klabsiella strains.
原文链接:- NSTL
- Elsevier
