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Structural and Electrical Properties of Niobium Doped Y0.6Gd0.4Ba2-xNbxCu3O7-y Superconductors  [PDF]
Mucahit Yilmaz, Oguz Dogan
Materials Sciences and Applications (MSA) , 2011, DOI: 10.4236/msa.2011.28147
Abstract: Polycrystalline samples of Y0.6Gd0.4Ba2-xNbxCu3O7-y(YGBNCO) with different Nb contents (x = 0.05, 0.10, 0.15, 0.20, and 0.25) were prepared using the usual solid state reaction technique. The structure for all samples was characterized by XRD and SEM. The electrical properties were measured by the FPP method in the temperature range from 70 to 130 K. The lattice constant of b remains almost unchanged and a and c increases with the increase of Nb content with x ≤ 0.10. The zero resistance transition temperature and Jc decrease with increasing Nb content. But superconductivity did not suppress. As the Nb content in the samples increases, it gives a diffused phase indicating a niobium perovskite phase and it is a small amount of unidentified phase.
Electrical, Structural and Morphological Properties of Sb-Doped Bi-Based Superconductors  [PDF]
Ghazala Y. Hermiz, Amal K. Jassim, Saad F. Oboudi
Advances in Materials Physics and Chemistry (AMPC) , 2015, DOI: 10.4236/ampc.2015.56022
Abstract: In this paper, samples of antimony doped Bi-based superconductor with stoichiometric composition Bi1.7Pb0.2Sb0.1Sr2Ca2Ca3O10 were prepared by a solid state reaction method. The effect of sintering time on the superconducting properties was studied; all samples were sintered in air at 850°C for different sintering time (80, 100, 120, 140, and 160) h. X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements were performed for determination of the crystal structure and surface morphology of samples, respectively. All samples showed an orthorhombic structure with two phases, high-Tc phase (2223) and low-Tc phase (2212) in addition to an impure phase. It has been observed that the critical temperature and the high-Tc phase increases and appears to be the dominant phase when the sintering time is increased to 140 h, while with increasing sintering time to 160 h, both Tc and the high phase started to decrease. (SEM) results show that increasing sintering time enhances the growing of superconducting phase unidirectional and suppresses the high phase intrusion which leads to the production of nearly single Bi-2223 phase with higher Tc.
Influence of O2/Ar ratio on the properties of transparent conductive niobium-doped ZnO films
Feng Cao,YiDing Wang,KuiXue Liu,JingZhi Yin,BeiHong Long,Li Li,Yu Zhang,XiaMei Chen
Chinese Science Bulletin , 2009, DOI: 10.1007/s11434-009-0377-y
Abstract: Niobium-doped ZnO transparent conductive films are deposited on glass substrates by radio frequency sputtering at 300°C. The influence of O2/Ar ratio on the structural, electrical and optical properties of the as-deposited films is investigated by X-ray diffraction, Hall measurement and optical transmission spectroscopy. The lowest resistivity of 4.0×10 4 Ω·cm is obtained from the film deposited at the O2/Ar ratio of 1/12. The average optical transmittance of the films is over 90%.
A Structural Probe of the Doped Holes in Cuprate Superconductors  [PDF]
P. Abbamonte,L. Venema,A. Rusydi,G. A. Sawatzky,G. Logvenov,I. Bozovic
Physics , 2002, DOI: 10.1126/science.1070903
Abstract: An unresolved issue concerning cuprate superconductors is whether the distribution of carriers in the CuO(2) plane is uniform or inhomogeneous. Because the carriers comprise a small fraction of the total charge density and may be rapidly fluctuating, modulations are difficult to detect directly. Here we demonstrate that in anomalous x-ray scattering at the oxygen K edge of the cuprates, the contribution of carriers to the scattering amplitude is selectively magnified 82 times. This enhances diffraction from the doped holes by more than 10^3, permitting direct structural analysis of the superconducting ground state. Scattering from thin films of La(2)CuO(4+x) (Tc = 39 K) at T=(50 +/- 5) K on the reciprocal space intervals (0,0,0.21) -> (0,0,1.21) and (0,0,0.6) -> (0.3,0,0.6) show a rounding of the carrier density near the substrate suggestive of a depletion zone or similar effect. The structure factor for off-specular scattering was less than 3x10-7 e, suggesting an absence of in-plane hole ordering in this material.
Structural study on hole-doped superconductors Pr1-xSrxFeAsO  [PDF]
J Ju,Z Li,G Mu,H-H Wen,K Sato,M Watahiki,G Li,K Tanigaki
Physics , 2009, DOI: 10.1088/1367-2630/11/8/083003
Abstract: The structural details in Pr1-xSrxFeAsO (1111) superconducting system are analyzed using data obtained from synchrotron X-ray diffraction and the structural parameters are carefully studied as the system is moving from non-superconducting to hole-doped superconducting with the Sr concentration. Superconductivity emerges when the Sr doping amount reaches 0.221. The linear increase of the lattice constants proves that Sr is successfully introduced into the system and its concentration can accurately be determined by the electron density analyses. The evolution of structural parameters with Sr concentration in Pr1-xSrxFeAsO and their comparison to other similar structural parameters of the related Fe-based superconductors suggest that the interlayer space between the conducting As-Fe-As layer and the insulating Pr-O-Pr layer is important for improving Tc in the hole-doped (1111) superconductors, which seems to be different from electron-doped systems.
Investigation of Niobium (Nb) Substitution on Structural and Superconducting Properties of (Bi, Pb)-Based Superconductors  [PDF]
Reza Asghari, Hasan Sedghi, Leyla ?olakerol Arsalan, Hamid Naghshara
Advances in Materials Physics and Chemistry (AMPC) , 2017, DOI: 10.4236/ampc.2017.77022
Abstract: In this study, the effects of Nb substitution on the Bi-based superconducting materials have been investigated. The X-ray diffraction measurement indicated coexistence of Bi-2212, Bi-2223 phases and some impurity phases of CuO, CuNb2O6, CaNb2O6, CaCuO2, and Sr5Nb5O16. With increasing Nb content, impurity phases consistent with the Nb element appeared in the samples. Also with increasing Nb content, the Bi-2223 phase of samples gradually was decreased and in contrast, the Bi-2212 phase was increased. From the SEM, results have been seen that with increasing of Nb contents, the crystal structure of the samples was slightly changed because of the disrupted grain growth. From the electrical resistivity measurements, it has been found that with increasing of Nb contents, critical temperature decreases and the superconducting transition width (ΔT) increases. Estimated critical current density showed that Jc decreases with increasing Nb content, as expected.
The structure of niobium-doped MoSe2 and WSe2
Moussa Bougouma, Boubié Guel, Tiriana Segato, Jean B. Legma, Marie-Paule Delplancke Ogletree
Bulletin of the Chemical Society of Ethiopia , 2008,
Abstract: Polycrystalline niobium-doped molybdenum and tungsten diselenides were synthesized in silica tubes sealed under secondary vacuum. They were characterized by scanning electron microscopy, electron diffraction, X-ray diffraction, chemical composition and EDX analyses. The morphology of niobium-doped molybdenum solid solutions was shown to depend strongly on the conditions of synthesis, whereas the structural characterization did not. KEY WORDS: Polycrystalline niobium-doped molybdenum and tungsten diselenide solid solutions, Doped powders diselenides, Mo1-xNbxSe2, W1-xNbxSe2, SEM, X-ray diffraction, Electron diffraction Bull. Chem. Soc. Ethiop. 2008, 22(2), 225-236.
Structural, Optical, Electrical, and Photoresponse Properties of Postannealed Sn-Doped ZnO Nanorods  [PDF]
Q. Humayun,M. Kashif,U. Hashim
Journal of Nanomaterials , 2013, DOI: 10.1155/2013/792930
Abstract: Tin (Sn) doped ZnO nanorods were synthesized on glass substrate using a sol-gel method. The synthesized nanorods were postannealed at 150, 350, and 500°C. The surface morphologies of Sn-doped ZnO nanorods at different postannealing temperatures were studied using scanning electron microscope (SEM). XRD results show that as the postannealing temperature increased from 150°C to 500°C, the c-axis orientation becomes stronger. Refractive indices and dielectric constants were calculated on the basis of different relationships by utilizing bandgap values. These bandgap values were obtained in terms of optical absorption by using a UV-Visible spectrophotometer. The enhancing effects of annealing temperatures on electrical properties were observed in terms of current-to-voltage measurements. Resistivity decreases as postannealing temperature increases from 150°C to 500°C. Annealed samples were evaluated for UV-sensing application. The samples exhibit a responsivity of 1.7?A/W. 1. Introduction Zinc oxide is an n-type semiconductor with bandgap energy of 3.37?eV and large exciton binding energy of ~60?meV. ZnO and its alloys are having vast device applications such as light emitting diodes (LEDs), solar cells, and optical waveguides [1–3]. ZnO is nontoxic, highly transparent along with high mechanical and thermal stability. Several researchers explore that the dopants can improve the electrical and optical properties of ZnO such as Al, In, and Sn [4–6]. When Sn was added into ZnO for doping, Sn+4 substitutes Zn+2 site in the ZnO crystal structure resulting in two more free electrons to contribute to the electric conduction [7]. The ionic radius of Sn+4 (0.069?nm) is smaller than Zn+2 (0.074?nm); therefore, Sn+4 ions can replace Zn+2 ions in substitution sites [8]. ZnO can be prepared by varieties of different techniques such as pulsed laser deposition (PLD) [9], RF sputtering [10], chemical vapor deposition (CVD) [11], sol-gel [12], metal organic chemical vapor deposition (MOCVD) [13], and molecular beam epitaxy (MBE) [14]. Among them, sol-gel is the mostly used technique for ZnO preparation; it is low cost, needs low temperature, and can be implemented for large-scale preparation as compared to other techniques [15]. In the present study, Sn-doped ZnO nanorods were successfully synthesized using sol-gel method. We also investigated the effects of postannealing temperatures on structural, optical, electrical, and photoresponse properties. The results of this investigation contribute to the application of synthesized nanostructures in optical devices and
Study of Electrical, Optical and Structural Properties of Al- Doped ZnO Thin Films on PEN Substrates  [PDF]
Mohit?Agarwal,Pankaj?Modi,R.O.?Dusane
Journal of Nano- and Electronic Physics , 2013,
Abstract: Aluminum-doped zinc oxide (AZO), as one of the most promising transparent conducting oxide (TCO) material, has now been widely used in thin film solar cells. Most of the study of AZO films till date has been done on glass substrates but nowadays there is a growing interest in replacing glass with polymer substrate for the thin-film solar cell technology and many other flexible optoelectronic devices. In this study, AZO thin films were deposited at room temperature by RF magnetron sputtering on flexible substrates from a 3 inch diameter target of 2 wt % Al2O3 in zinc oxide. The effect of RF power on the structural, optical and electrical properties of AZO films was investigated by X-ray Diffraction (XRD), Hall measurement, and UV-visible spectrophotometery. The XRD data indicates a preferential c-axis orientation for all the films. All films exhibit high transmittance ( 85%) in visible region. Films deposited at 60 W power exhibit lowest resistivity of 1.2 10 – 3 Ω cm.
Structural, Optical, and Electrochromic Properties of Pure and Mo-Doped WO3 Films by RF Magnetron Sputtering  [PDF]
Vempuluri Madhavi,Paruchuri Kondaiah,Obili Mahammad Hussain,Suda Uthanna
Conference Papers in Science , 2013, DOI: 10.1155/2013/104047
Abstract: Pure and Mo-doped WO3 films were formed on ITO-coated glass substrate held at 473?K by RF magnetron sputtering technique. The structural, morphological, and optical properties of pure and Mo-doped WO3 thin films have been systematically studied. The structural properties revealed that the pure WO3 films exhibited a (020) reflection related to the orthorhombic phase of WO3, whereas Mo-doped films showed (200) reflection. The surface morphology revealed that pure WO3 films showed the dense surface and Mo-doped films contained agglomerated grains which were uniformly distributed on the surface of the substrate. The optical transmittance decreased from 85% to 75% for pure and Mo-doped WO3 films, respectively. The electrochromic properties of the films were measured by cyclic voltametry in 1?M Li2SO4 electrolyte solution. The optical modulation of pure WO3 films at near IR was 50%, and the calculated color efficiency was 33.8?cm2/C, while in Mo-doped WO3 the efficiency improved to 42.5?cm2/C. 1. Introduction Tungsten oxide (WO3) is the most widely used electrochromic material because of easiness in synthesis and favorable electrical and optical properties. The application of electrochromic materials for smart windows, displays, and antiglare mirrors and several applications have been developed such as control of incoming daylight into buildings, smart windows, rearview mirrors, and aphotochromic and electrochromic devices [1–3]. Tungsten oxide is the extensively studied electrochromic material [4, 5]. Doping of vanadium, niobium, nitrogen, titanium, or nickel to WO3 enhances in the electrochromic properties. Muthu Karuppasamy and Subramanyam [6] reported that the color efficiency decreased from 121 to 13?cm2/C with increase of vanadium doping of 9 at. % in tungsten oxide films deposited by DC magnetron sputtering. Bathe and Patil [7] studied the electrochromic properties of niobium-doped WO3 films, and the coloration efficiency decreased with the increase of niobium doping. Sun et al. [8] studied the nitrogen-doped WO3 films formed by reactive DC pulsed sputtering and the color efficiency achieved to 45?cm2/C at 5 at. % nitrogen doped films. Karuppasamy and Subrahmanyam [9] studied the electrochromic properties of titanium doped tungsten oxide films and realized the improvement in the electrochromic properties with the increase of titanium doping. Gesheva et al. [10] studied MoO3-WO3 films formed by chemical vapour deposition method and showed the color efficiency of 141?cm2/C when compared to 84?cm2/C for WO3 and 39?cm2/C for MoO3 films. Valyukh et al. [11]
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