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[en] The original version of this article unfortunately contains errors in Abstract, Section 4.4 Vickers microhardness test and Section 5 Conclusion. In Abstract (7th line) the word “hard” should be changed to “soft”, in Section 4.4 Vickers microhardness test, 15th line the value 1.04 should be changed to 3.27 and in the same sentence the word “hard” should be changed to “soft”. In Section 5 Conclusion (18th line) the word “hard” should be changed to “soft”.
[en] The article titled “Strontium-substituted La0.75Ba0.25−xSrxFeO3 (x = 0.05, 0.10 and 0.15) perovskite: dielectric and electrical studies”, written by F. B. Abdallah, A. Benali, S. Azizi, M. Triki, E. Dhahri, M. P. F. Graça, M. A. Valente, was originally published electronically on the publisher's internet portal (currently SpringerLink) on March 2019 with open access.
[en] Methylammonium (MA) and formamidinium (FA) lead trihalide perovskites, such as MAPbI3, and FAPbI3 materials are propitious contenders for solar cells and photovoltaic functionalities because they illustrate band gaps of about 1.5 eV or more. Herein, we scrutinized the electronic structures and optical features of MAPbI3 and FAPbI3 halide perovskites using full-potential linearized augmented plane-wave calculations. The structural parameters were acquired using the generalized gradient approximation. The FAPbI3 halide perovskite was found to display lower stability than the MAPbI3 material. The total and partial density of states (DOS) were established for these two halide perovskites, in order to reveal the DOS localization for each atomic element by employing the modified Becke–Johnson (TB-mBJ) potential for the exchange–correlation term. The overall optical spectra were also examined over photon energy for these promising systems, involving the dielectric function, absorption coefficient, optical reflectivity, refractive index, and electron energy-loss function. The results of our theoretical investigations are in accordance with the currently published experimental evidence and should be effective in generating novel materials with tremendous functionalities in photovoltaic devices.
[en] We present a facile and low-cost in-situ growth of Ni(OH)2–NiFe2O4 nanosheet arrays on nickel foams via one-pot hydrothermal process. Different amounts of Fe(NO3)3 solutions as the oxidant have been used to optimize morphology of the nanosheet arrays on nickel foams without any templates and nickel salts. The nanosheet arrays show excellent electrochemical stability as well as good electroconductivity. As an electrochemical electrode, it presents an optimized areal capacitance (1.434 F cm−2 at the current density of 1.0 mA cm−2) and excellent cycling stability (retaining 75.9% after 5000 cycles at 3.0 mA cm−2). This strategy holds great potential for low-cost and readily scalable production of high performance electrode materials for supercapacitors.
[en] Pure and dual doped ZnO nanoparticles were synthesized via the wet chemical method. The synthesized samples were characterized by XRD, HR-SEM/EDS, HR-TEM, UV–Vis, PL, FT-IR, and FT-Raman spectral measurements. The prepared ZnO nanoparticles exhibit a hexagonal wurtzite structure and [Ce–La, La–Gd, Gd–Ce] rare earth dual doped ZnO nanoparticles was confirmed from the shift in XRD peaks position, cell parameter and also changes in the peaks intensity. HR-SEM/EDS and HR-TEM show spherical in shape with less agglomeration on the surface of all samples and the images are clearly revealed that the particle size ~ 40 nm (PZ), 14 nm (ZCL3), 16 nm (ZLG3) and 28 nm (ZGC3). UV–Vis spectra show a strong Ultraviolet region absorbance for ZCL3 sample with the low Energy band gap value of 2.81 eV. The presences of the functional group and molecular vibrations are characterized by employing the FT-IR and FT-Raman spectra. From the PL spectra, it was found that the peak position of all samples produces a visible emission. The photocatalytic performance of the synthesized doped nanoparticles found to exhibit better degradation of MB dye under solar irradiation ZCL3 showed an increase in the photo catalytic decolorization efficiency. The bactericidal activity of dual doped ZnO nanoparticles was investigated against Gram-positive and Gram-negative bacteria and compare with standard ampicillin. We observe that ZCL3 sample have excellent antibacterial activity against Gram-negative bacteria (P. mirabilis) and the mean zone of inhibition ~ 20 mm.
[en] The structural properties of AlN/GaN multiple quantum well (MQW) structures grown on c-plain sapphire substrate are studied by means of high-resolution X-ray diffraction (HRXRD). A new method to consider the influence of the depth variation of the dislocations density and well (barrier) thicknesses on the X-ray diffraction spectra was developed. The influence of the dislocation type on the diffraction peak broadening is based on the mosaic model of a crystal. The represented simulations of the experimental spectra are based on the dynamical theory of X-ray diffraction in agreement with the developed model. The calculations of X-ray diffraction spectra for AlN/GaN MQW considering the depth variation of dislocation density and layers thicknesses explain well the observed broadening and asymmetry of the satellites peaks of the measured spectra, especially for higher-order reflections. In addition, in this paper was demonstrated, that the commonly used Williamson–Hall plot analysis is consistent for MQW structures with the dislocations density > 1 × 108 cm−2. The developed methods allow fast and reliable determination of layers thicknesses, dislocations densities and strain profiles.
[en] The switching characteristics of rare element Ce-doped HfOx films were investigated. The effect of Ce doping on oxygen defects was analyzed by X-ray photoelectron spectroscopy (XPS) and first-principle calculations. The variations of valence state of Ce and oxygen vacancies with the increase of Ce doping concentration were demonstrated. Although Ce doping increased dopants-induced oxygen vacancies in HfOx film, the density of oxygen vacancies decreased as the doping concentration increased. Besides, the introduction of Ce dopants enlarged the difference in electronegativity of Hf and O which made it harder for O to escape from HfOx film under voltage. Hence the switching behaviors of Ce-doped HfOx film were affected by multiple factors and can be effectively improved with an appropriate doping concentration (4.3%). A physical model based on the formation and rupture of conductive filaments was proposed to clarify the switching behavior of Ce-doped HfOx samples.
[en] LiCoO2 powders are the popular active cathode material in lithium batteries, but their dielectric and microwave absorption properties were seldom reported. In this work, the LiCoO2 powders were synthesized by solid-state reaction. And in order to enhance their dielectric properties, influence of metal ions micro-dopant on the electromagnetic property of LiM0.94Co0.06O2 powders (M = Mg, Zn, Ni, Mn and Y) was investigated. The phase and composition were characterized. The dielectric properties and the microwave absorption properties were evaluated. Compared to dopant of Zn, Ni, Mn and Y ions, the results showed that both the real part (ε′) and imaginary part (ε″) of LiM0.94Co0.06O2/paraffin mixtures were obviously increased by doping Mg ions. One layer absorbent with 75 wt% LiMg0.06Co0.94O2 content of a thickness of 1.8 mm had the optimum microwave absorption properties. The lowest reflection loss was − 36.6 dB. The results indicated that LiCoO2 and LiM0.06Co0.94O2 powders would be a possible candidate for microwave absorption materials.