oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Structural and Electrical Characterization of Sintered Silicon Nitride Ceramic  [PDF]
Imran Khan, M. Zulfequar
Materials Sciences and Applications (MSA) , 2011, DOI: 10.4236/msa.2011.27102
Abstract: The electrical conduction phenomena, dielectric response and microstructure have been discussed in sintered silicon nitride ceramics at different temperature and frequencies. Microstructure and phase of the sintered samples was investigated by Scanning Electron Microscope (SEM) and X-ray diffractometer (XRD). The electrical conductivity, dielectric constant and dielectric loss increases exponentially with temperature greater than 600 K. The dielectric constant and loss have been measured in the frequency range 100 Hz to 1 MHz. The a.c. conduction studies in the audio frequency range 500 Hz to 1 MHz indicates that the conduction may be due to the electronic hopping mechanism. Silicon Nitride ceramics became dense after sintering. The effect of grain size and role of phase on electrical and dielectric properties have been discussed. These types of samples can be used as a high temperature semi conducting materials for device packaging.
The Effects of Magnetic Dopant on the Structural and Electrical Properties in Superconducting YBaCu3O7-δ Ceramic  [PDF]
Souheila Chamekh, Abderrahmane Bouabellou
Advances in Chemical Engineering and Science (ACES) , 2018, DOI: 10.4236/aces.2018.81001
Abstract:
The work reported in this paper aims at a better understanding of the magnetic doping effects on the structural and electrical properties for a series of YBa2(Cu1-xCox)3O7-δ ceramics. The Co doped YBa2Cu3O7-δ are (YBCO) prepared by conventional solid state reaction method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), differential thermal analysis (DTA) and resistivity measurements. The crystal lattice parameters are found to change due to the cobalt doping and tendency to a structure phase transition from orthorhombic to tetragonal, which is confirmed by the decrease of the degree of orthorhombicity. The morphology examination with SEM revealed gradual increases of grain size with x = 0.02 Co, a high porosity is observed in the doped samples compared to the pure one. The decomposition temperature of YBCO is pushed from temperatures above 975°C to lower temperatures of 945°C. The resistivity measurements of doped samples with x = 0.04 and 0.06; shows a deviation in from T-linear behavior due to the opening of a pseudogap.
STRUCTURAL, DIELECTRIC, FERROELECTRIC AND MAGNETIC PROPERTIES OF MN-DOPED BIFEO3 NANOPARTICLES SYNTHESIZED BY SOL-GEL METHOD  [PDF]
Ghanshyam Arya,Ashwani Kumar,Mast Ram,Nainjeet Singh Negi
International Journal of Advances in Engineering and Technology , 2013,
Abstract: BiFe1-xMnxO3 (x = 0.0–7.5%) nanoparticles were successfully synthesized by tartaric acid assisted sol-gel method followed by rapid cooling process. XRD patterns indicate secondary phases in pure BiFeO3 (BFO) which get suppressed with Mn concentration up to 5%. The observation of absorption peaks at 559 cm-1 and 432 cm-1 in FTIR spectra confirms the formation perovskite structure. The Mn substitution at B-site of BFO improves the particles surface morphology and reduces the average particles size to around 65nm. Dielectric constant increases from 19 for pure BFO to 46 for 5% composition while their loss tangent decreases from 0.2 to 0.016, respectively. A small dielectric relaxation peak is observed for 2.5% composition which disappears for 5% due to reduction of charged defects such as oxygen ion vacancies. The ferroelectric behavior improves with Mn-doping and maximum remnant polarization value of 1.8μC/cm2 at a maximum applied field of 80kV/cm is observed for 5% composition. Enhanced magnetic property is observed for different Mn contents with maximum value of saturation magnetization of 0.20emu/g at room temperature.
Y-Co共掺BiFeO3粉体的结构和多铁性研究
Structural and multiferroic properties of (Y,Co) co-doped BiFeO3 nanoparticles
 [PDF]

束华中,毛巍威,宋荣方,李兴鳌
- , 2017,
Abstract: 采用溶胶 凝胶工艺制备了纯BiFeO3(BFO)、A位钇掺杂Bi0.95Y0.05FeO3(BYFO)、B位钴掺杂BiFe0.95Co0.05O3(BFCO)、以及A和B位钇钴共掺杂Bi0.95Y0.05Fe0.95Co0.05O3(BYFCO)纳米粒子,并对样品的结构和形貌以及多铁性能进行了系统的研究。结果表明不论是A位掺杂,还是B位掺杂,对BFO的铁电和铁磁性能都有很大的提高,而A和B位钇钴共掺取得了最好的铁电和铁磁性能。与纯BFO样本相比,BYFCO样本的漏电流密度降低两个数量级,而剩磁(Mr)达到0.085 emu/g。Y-Co共掺杂BYFCO纳米粒子被证明是一种提高BFO多铁性能的有效方法。
The pure BiFeO3(BFO),A-site Y single-doped Bi0.95Y0.05FeO3(BYFO),B-site Co single-doped BiFe0.95Co0.05O3(BFCO) and A/B-site (Y,Co) co-doped Bi0.95Y0.05Fe0.95Co0.05O3(BYFCO) nanoparticles are prepared by a sol-gel method.The crystal structure and multiferroic properties of the samples are systematically investigated.Results show that all the A/B-site single-doped and co-doped BFO samples can improve ferroelectric and ferromagnetic properties,A/B-site co-doped BYFCO sample can achieved the best ferroelectric and ferromagnetic properties.Compared with the pure BFO sample,the leakage current density of the BYFCO sample decreases about two orders of magnitude.The remanent magnetization (Mr) of the BYFCO sample reaches 0.085 emu/g.The (Y,Co) co-doped BFO nanoparticles has been proved to be an effective method for improving the multiferroic properties
A Study on Structural, Optical, Electrical and Etching Characteristics of Pure and L-Alanine Doped Potassium Dihydrogen Phosphate Crystals  [PDF]
Ferdousi Akhtar, Jiban Podder
Journal of Crystallization Process and Technology (JCPT) , 2011, DOI: 10.4236/jcpt.2011.13009
Abstract: Pure potassium dihydrogen phosphate (KDP) crystals and KDP doped with L-alanine have been grown by slow evaporation technique at room temperature. Grown crystals have been characterized using powder X-ray diffraction, (XRD), Energy Dispersive X-ray spectroscopy (EDX) and Fourier Transform Infrared spectroscopy (FTIR). The presence of L-alanine into pure KDP crystal was confirmed by FTIR and EDX spectra. Crystal structure has been studied by XRD. Pure KDP and L-alanine doped KDP crystals both possessed tetragonal structure. The transparency is found to increase with the increase of doping concentrations of the grown crystals as observed by UV-Vis spectra. A.C. electrical conductivity of grown crystals along the growth axis was carried out at various temperatures ranging from 35?C - 400?C. Dielectric constant and dielectric losses are measured as a function of temperature and this study reveals the contribution of space charge polarization. Crystal defects and surface morphology are studied by dissolution solvent technique and reveals the step growth mechanism for both pure and doped crystals.
Structural, Optical, Electrical and Thermal Characterizations of Pure and L-alanine Doped Ammonium Dihydrogen Phosphate Crystals  [PDF]
Ferdousi Akhtar, Jiban Podder
Journal of Crystallization Process and Technology (JCPT) , 2011, DOI: 10.4236/jcpt.2011.12004
Abstract: Pure ammonium diyidrogen phosphate and L-alanine doped ammonium diyidrogen phosphate crystals were grown from aqueous solutions by natural evaporation process. The grown crystals are characterized by Fourier Transform Infrared spectroscopy, Energy Dispersive X-ray, UV-visible spectroscopy and differential thermal analysis. Crystal structure has been studied by powder X-ray diffraction. Pure and doped crystals both possessed tetragonal structure. The optical transparency is found to increase with the increase of doping concentration in the grown crystals and band gap energies of all crystals have been calculated at their cut off frequencies. It is found that the optical band gap increases with doping concentrations. D.C.electrical conductivity of grown crystals along the growth axis was carried out at temperatures ranging from 35-140°C by the conventional two-probe method. The conductivity of the crystals increases with temperature and also increases with the L-alanine concentration. The decomposition temperatures and weight loss have been estimated from the Thermo Gravimetric Analysis and Differential Thermal Analysis and hardness was found from the Vicker’s microhardness measurement.
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
Pr and Cr co-doped BiFeO3 nanotubes: an advance multiferroic oxide material  [cached]
Das Rajasree,Gopal Khan Gobinda,Mandal Kalyan
EPJ Web of Conferences , 2013, DOI: 10.1051/epjconf/20134015015
Abstract: Arrays of single phase pure and Pr-Cr co-doped BiFeO3 (BFO) nanotubes (NTs) with compositions BiFeO3 and Bi0.9Pr0.1Fe0.9Cr0.1O3 have been synthesized using Anodic Aluminium Oxide (AAO) template (pore diameter ~250 nm) by wet chemical liquid phase deposition technique. All the NTs show ferromagnetic nature at room temperature (RT). Better magnetic properties are observed in the co-doped BFO NTs with the value of saturation magnetization (MS) ~49 memu/g, magnetization at the remanence (MR) ~12 memu/g and coercive field (HC) ~103 Oe. Increase of ferromagnetic signature in the co-doped BFO NTs is believed to be due to the collapse of the space-modulated spin structure. Significant increase in the dielectric characteristics in co-doped BFO NTs suggests lowering of leakage current due to the reduction of the oxygen vacancies in the structure. Strong Magnetodielectric effect (MD), expressed by [εr(H)-εr(0)]/εr(0) is observed in doped BFO NTs, where the increase of the dielectric constant is noticeable with the increase in the applied magnetic field. The codoped BFO NTs show noticeable increase in MD effect at a lower field (1-2 kOe).
Spectroscopic ellipsometry, optical, structural and electrical investigation of sprayed pure and Sn-doped ZnO thin films  [cached]
Mokhtari H.,Benhaliliba M.,Aida M.S.,Attaf N.
EPJ Web of Conferences , 2013, DOI: 10.1051/epjconf/20134403006
Abstract: In this work, we report the transparent pure and Sn-doped zinc oxide (ZnO). The films were deposited onto microscope glass substrate which was heated at 350±5C° by ultrasonic spray pyrolysis (U S P) deposition technique. The concentrations of Sn were selected within the range of 0-3% by step of 0.5% and the time deposition is kept at 5 min. A (002)-oriented wurtzite crystal structure was confirmed by X-rays patterns; and grain size varied within the range 7.37-14.84nm, and cristanillity is calculated goes from14.4 to 45.9%. Based on UV-VIS-IR analysis, the results revealed the high transparency of the sprayed films which exceeds 90%. The band gap energy was of 3.26-3.30 eV. The film thickness was estimated by spectroscopy ellipsometry and the found values were of 165-270nm. The refractive index is in the range of 2.75.The obtained electrical parameters were around 1018 cm 3, 3.6 cm2/Vs, 1.6Ω.cm; 5.8cm3/C. finally the Sn-doping has influenced the physical parameters of asground ZnO films
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.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.