جستجوی مقالات مرتبط با کلیدواژه « خواص ساختاری » در نشریات گروه « فیزیک »

In this research, the structural features, electronic and magnetic properties of armchair (5, 5) indium phosphide nanotube doped with Cr, Co, Cu and Zn have been investigated using first principles calculations. Calculations were performed by the PWscf code using a density functional theory. The metals Cr, Co, Cu and Zn were replaced by P atomic position in this nanotube. The optimal angles between them and the bond length were calculated. The calculations illustrate that there is a structural distortion around Cr and Co impurities, and also show that the magnetic moments are consistent with the predicted value of Hund’s rule. Furthermore, the observations revealed that the indium phosphide nanotube doped with Cr and Co is a ferromagnetic metal, while the indium phosphide nanotube doped with Cu and Zn is a non-magnetic metal. The present results predict that indium phosphide nanotubes doped with Cr and Co are useful for industrial applications in Nano magnets. To identify the most stable configuration, the binding energy and the cohesive energy were calculated for all compounds. Finally, our results show that the InP nanotube doped with Cobalt is more stable than others

Abstract In this article‚ bismuth ferrite nanoparticles (BiFeO3) were prepared by sol-gel method. To determine the sintering temperature range of bismuth ferrite nanoparticles, thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were performed on its dry gel. In order to improve structural and optical properties, samples sintered at temperatures of 600‚ 650,700,750, 800 and 850 °C. Then‚ structural and optical properties of the samples have been investigated of by X-ray diffraction (XRD)‚ Fourier transform-infrared spectroscopy (FT-IR),Field emission scanning electron microscopy (FESEM)‚ Ultraviolet-visible spectroscopy analysis (UV-Vis) and Photoluminescence analysis (PL). The result of XRD and FT-IR analysis showed that samples have distorted perovskite structure. FESEM images indicated that by increasing sintering temperature‚ the size of nanoparticles increases. UV-Vis and PL analysis showed that samples are semiconductor and have an energy gap of about 2 (ev).

In this article, we present fabrication and characterization of two-layered polymer light emitting diode (PLED) with a structure of ITO/PEDOT:PSS/MEH:PPV/Al which emits a orange-colored light, with the aim of reduction of lightening voltage. In this work, the PEDOT:PSS layer, as hole injection layer, was coated with spin coating method and a rotating speed of 2000 rpm and the MEH:PPV layer, as an active layer (emission layer), was coated with four rotating speeds. The impact of change in layer thickness on the surface roughness, optical absorption, and most importantly, the lightening voltage was investigated. Eventually, a PLED with a structure of ITO/PEDO:PSS(2000 rpm)/MEH:PPV(6000 rpm)/Al (165 nm) was selected as the optimum structure with a minimum lightening voltage of 7.1 V. The emission light ranged from 550 nm to 650 nm and was observed as an orange light.

In this paper, strontium spinel ferrite (SrFe2O4) nanoparticles were prepared by sol-gel method. Also, in order to the effect of sintering time on the structural, magnetic and dielectric properties of SrFe2O4 nanoparticles, first, the gel of the metal nitrates with certain molar ratio prepared and then the prepared powders were calcined at 700 ℃ with different times. The results of XRD show that the main phase of SrFe2O4 increase by increasing sintering times. Also, the FESEM images of the samples show that the particles of SrFe2O4 are homogeneous, but as the samples have magnetic properties, thus agglomeration of them have been occurred. The results of the samples FT-IR show that the sites of tetrahedral and octahedral which are important properties of ferrites were formed. The magnetic properties of the samples show that by increasing the sintering time, the amount of Ms and Hc has been increased which these changes are due to the distribution of ions and shape anisotropy of the nanoparticles. The results of the measurements of dielectric of the samples show that the both ε and for the samples decrease rapidly with increasing applied field frequency, while the ac electrical conductivity has been increased.

In this research the effect of substrate temperature and also annealing treatment at sulfur atmosphere on structural, surface morphological, optical, electrical and thermoelectrical properties of molybdenum trioxide/molybdenum disulfide (MoS2/MoO3) compound thin films were studied. The XRD patterns analysis indicated the formation of crystallite structure with two MoO3 orthorhombic and MoS2 hexagonal phases. After sulfurization process, the peaks of oxide phase disappeared and MoS2 single phase structure formed. FESEM images indicated surfaces that was coated uniformly with spherical shaped particles. All samples had an absorption coefficient about 104 cm-1 and their band gap energy after sulfurization significantly reduces in average from 2.60 to 1.55 eV. Hall effect data showed that MoS2 thin films had hole conduction type (in agreement to trend of variation of Seebeck coefficient) and also hole density in order of 1015 cm-3.

In this study, we investigate the electromagnetic wave absorption of Hard-Soft ferrite nanocomposites in the frequency range of 1-18 GHz. These composites consist of two different magnetic phases with different weight ratios. The hard magnetic phase consists of Strontium Hexaferrite (SF) and the soft magnetic phase consists of Cobalt Zinc Ferrite (CZF). XRD analysis of the samples indicate formation of pure phase for each magnetic phases. Investigation of the real and imaginary parts of complex permittivity and permeability of samples indicate the response of electromagnetic waves to these samples in the frequency range of 1-18 GHz. The reflection loss versus frequency shows this absorbing behavior in the samples.

In this work,the physical properties of KTP and RTP single-crystals have been investigated by performing accurate total energy calculations in the framework of density functional theory by using the full-potential linearized augmented plane wave method. The effects of Rb substitution on structural, electronic and optical properties of KTP are discussed. The structural properties have been calculated by using different exchange correlation including LDA, PBE, WC and PBEsol. Also PBEsol approximation and and more accurate approximation mBJ are employed to calculate the energy gap values. The Pseudoinversion values of both crystals have been calculated by using PseudoSymmetry software . Rb substitution effect on pseudosymmetry of KTP and also relation between second-order susceptibility of crystals and the Pseudoinversion values are discussed. The optical coefficients such as refractive index, birefringence values and absorption coefficients have been calculated by using the dielectric function. The anisotropy in the linear optical properties of KTP and RTP crystals have been demonstrated. Then calculated results have been compared.

In this paper, the stability, electronic and magnetic properties of rapheme nanoribbons with zigzag edge shape (ZGNR) doped by Fe atoms, using density functional theory (DFT) have been investigated. According to our investigations and obtained values for the formation and binding energy, the best situation for the substitution Fe atoms by carbon atoms found at the edge of ZGNR and with the carbon atoms which are bonded to the hydrogen atoms. Also if Fe atoms substituted to Hydrogen atoms instead of carbon atoms, the structure would be more energy desirable and when the structure doped by two Fe atoms in both ferro and anti ferromagnetic phases, close doping is more stable than far doping. The maximum magnetic moment is found about 5 B for Fe doping when substituted to Hydrogen atoms in F site. According to the electronic band structure calculations, the electronic and magnetic properties of ZGNR depend to situation of substituted Fe atoms and depending on what location were choose to replace the iron atoms, magnetic metal or magnetic semiconductors will be achieved.

Magnetite nanoparticles have been synthesized using sonoelectrooxidation of iron plate in an aqueous solution of electrolyte containing thiourea as organic stabilizer. The effect of applied current on structural and magnetic properties of nanoparticles was investigated. The particles structure was characterized using XRD, and SEM. Room-temperature magnetization curves of the samples obtained using a VSM. In order to study the stoichiometric property of the magnetite nanoparticles, Mössbauer spectra in transmission geometry were recorded for all samples. The X-ray patterns showed that the products have cubic spinel structure with space group. The SEM images showed that the particles with sizes in the range 25 to 50 nm depending on the applied current are grown. The room-temperature VSM results showed that all of the samples are magnetically soft and their specific magnetization depends on the mean particle size. Mössbauer spectra are well fitted with two magnetic sextets sub-spectra corresponding to Fe3+ ions at A sites (tetrahedral coordination) and Fe2.5+ ions at B sites (octahedral coordination) associated with magnetite structure. The chemical formula of samples was obtained by taking in to account the deficit of iron in their structure.