Papers by Keyword: Lattice Parameter

Abstract: Thin films CuInSe₂ (CIS) cells have been fabricated by the electro chemical method. Some of the physical properties such as lattice parameter, crystal structure and grain size of CuInSe₂ (CIS) films with different Cu/In ratios ( 0.50-1.1) were determined using X-ray diffractornetry. The surface morphology with different Cu/In ratios was studied using a scanning electron microscope. The SEM studies on these films showed that the grain size increases the Cu/In ratios increases from 0.49 to 1.1. The variation of the band gap with different Cu/In ratio was determined from optical absorption measurements. The results showed that the band gap decreases as the Cu/In ratio increases over the considered range of composition. Key words: Thin films, Lattice Parameter , Optical Absorption, grain size

Abstract: The radiation damage and its distribution in the type-Ib diamond film implanted by B ion have been investigated by means of Raman scattering and X-ray diffraction spectra. It is of significance during the applications of diamond materials due to several phenomena related to B-doped diamond, such as the superconductivity, the conversion of p-type to n-type conductivity and the low resistivity. The Raman scatting spectra indicated that the radiation damage in implantation layer was various with implantation depth. The top layer was damaged badly and graphitized completely. There existed small damage in nether layer, which resulted in partly amorphous carbon. It was noted that the volume was expanded in diamond film implanted by B ion. By x-ray diffraction pattern, it was reckoned that the lattice parameter was enlarged in B-implanting diamond layer, which expanded the volume of diamond film.

Abstract: ZnO belongs to the II-VI semiconductor group with a direct band-gap of 3.2-3.37 eV in 300K and a high exciton binding energy of 60 meV. It has good transparency, high electron mobility, wide, and strong room-temperature luminescence. These properties have many applications in a wide area of emerging applications. Doping ZnO with the transition metals gives it magnetic property at room temperature hence making it multifunctional material, i.e. coexistence of magnetic, semiconducting and optical properties. The samples can be synthesized in the bulk, thin film, and nanoforms which show a wide range of ferromagnetism properties. Ferromagnetic semiconductors are important materials for spintronic and nonvolatile memory storage applications. Doping of transition metal elements into ZnO offers a feasible means of tailoring the band gap to use it as light emitters and UV detector. As there are controversial on the energy gap value due to change of lattice parameters we have synthesized Mn-doped ZnO nanoparticles by co-precipitation method with different concentrations to study the effect of lattice parameters changes on gap energy. The doped samples were studied by XRD, SEM, FT-IR., and UV-Vis. The XRD patterns confirm doping of Mn into ZnO structure. As Mn concentrations increases the peak due to of Mn impurity in FT-IR spectra becomes more pronounces hence confirming concentrations variation. We find from UV-Vis spectra that the gap energy due to doping concentration increases due to the Goldschmidt-Pauling rule this increase depends on dopant concentrations and increases as impurity amount increases.

Abstract: The mineral or inorganic component of bone is a calcium phosphate idealized as a calcium hydroxyapatite, HA, Ca₁₀ (PO₄)₆(OH) ₂. Changes in the composition of the apatite affect its lattice parameters, morphology, crystallinity (reflecting crystal size and/or perfection) and finally dissolution properties. In regard to the above points, lattice parameters are expected to have better dissolution properties. Estimation of HA nanocrystallite size lattice parameters is one of the most important factors for dissolution properties of bone apatites. In present work, the composition of apatite induce complex structures at the unit-cell level and play a role in influencing the dissolution rate of apatites, which may favour osteointegration. The samples are consist of NHA, bovine bone heated at 850 °C for 3 h; BHA, human bone heated at 900 oC for 2 h and PHA, HA pure powder. The results estimated by XRD data indicate that increasing in c/a ratio of HA, which is leading to increasing in crystallinity, induce decrease at HA dissolution or improving its chemical solubility in simulated body fluid (SBF). As, it was concluded that the biodegradation of HA decrease in PHA sample.

Abstract: Ni-Cu-Zn ferrites with general formula Ni0.5Cux/2Zn0.5-x/2Fe2O4 (with x = 0.3, 0.4, 0.5 and 0.6) have been synthesized using oxalate precursor method with different precursor reaction temperatures in the range 100C to 700C. The structural analysis has been carried out using X-ray diffraction studies which reveal the formation of ferrites structure. The lattice parameters obtained using the most intense 311 peak are found to be in the range 8.37 to 8.42 Å for all the samples. The saturation magnetization is found to be in the range 20 to 51 emu/g, while the magnetic moment is found to be in the range 0.63 to 1.5 µB. The magnetic losses were found to be maximum for the samples obtained at precursor reaction temperature of 350C. The grain size is found to be in the range 0.4 to 2.0 µm. There is variation in the magnetic properties for different precursor temperatures indicating the effect of reaction history on the various parameters studied.

Abstract: Thin films of Cd_xZn_(1-x)S (0 x 1) were deposited on glass substrates by the chemical spray pyrolysis technique using a less used combination of chemicals. The variation of structural properties of these films in relation with composition was studied in detail. The entire study was made for a wide range of compositions of Cd_xZn _(1-x) S thin films (x=0 to 1 in steps of 0.1). XRD studies reveal that all the films are polycrystalline with hexagonal (wurtzite) structure of which reflection peaks associated with (100), (002) and (110) planes were clearly identified for all the films and inclusion of cadmium into the structure of ZnS improved the crystallinity of the films. The value of lattice constants a and c was found to vary with composition from 0.382 to 0.415 nm and 0.625 to 0.675 nm respectively.

Abstract: The purpose of this work is to understand the phases formation and lattice parameter changes with addition 0.6 to 2.7 wt.% in Al-Si-Mg-Ce cast alloy. Al-Si-Mg-Ce eutectic and hypoeutectic cast alloy were prepared by conventional casting technique. The alloys were investigated by using optical microscope, Scanning electron microscope (SEM) and X-Ray diffractometry (XRD). The addition of Ce resulted in precipitation of Al₄Ce in eutectic cast alloy and CeMg₂Si₂ in hypoeutectic cast alloy. The lattice parameter of Al increases with increase in Ce content wheareas lattice parameter of Si phase decreases as the Ce content increases.

Abstract: In order to synthesize morphology and structure-controlled nano-copper, chemical reduction synthesis method was used coalescing microwave-assisted and modification. Cu nanowires with diameters of 20 to 25nm and lengths of 1.2 to 2.1μm were yielded by reduction of copper acetate tetrahydrate of (1, 2)-propanediol system using ascorbic acid as a reductant, polyethylene sorbitan monooleate (Tween 80) as a modifier and by microwave-assisted heating. The microstructure of these nanowires has been characterized by XRD and TEM. The XRD patterns indicate that the lattice parameters of these Cu nanowires are enlarged about 1.162% while the lattice parameters of Cu nanospheres are reduced about 1.024%. The growth mechanism of Cu nanowires is also suspected. The anti--wear and reducing friction performance of liquid paraffin with either Cu nanowires or Cu nanospheres has been measured by ball--on--disk UMT--II tribometer. It is found that the tribological performance of liquid paraffin with nano-Cu is improved, and the enhancement of improvement with Cu nanowires is better than with Cu nanospheres.

Abstract: By means of different cooling methods, microstructure observation and X-ray diffraction analysis, an investigation has been made into the influences of the cooling methods on the microstructure and lattice parameters of FGH95 superalloy. The results shown that, after the solution treated alloy is cooled at different mediums, fine γ′phase and carbide particles dispersedly distribute in the grain and coarser γ′phase discontinuously precipitates along grain boundaries. After X-ray diffraction analyzed, the γ and γ′phases in “molten salt cooling” alloy possess larger lattice parameters, and a bigger lattice misfit exists in the interface between the γ and γ′phases.

Abstract: The geometry optimization, formation energy, Mulliken populations, and density of states of YAP (YAlO₃) crystal are studied by using first-principles method based on density functional theory. The optimal lattice parameters of YAP crystal are in good accordance with experimental results reported. The calculated formation energy (-3.73eV) indicates the excellent structural stability of YAP crystal. The obtained Mulliken charge populations of O, Al and Y atoms and their deviations from the formal ones, as well as overlap populations show YAP crystal is a mixed bond material with stronger ionic and weaker covalent bonds, which is attributed to the hybridization of atomic orbitals. The comprehensive effect of various interactions in the system makes YAP crystal more stable.