scholarly journals Effect of Tb-doped Concentration Variation on the Electrical and Dielectric Properties of CaF2 Nanoparticles

Nanomaterials ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 532 ◽  
Author(s):  
Xiaoyan Cui ◽  
Tingjing Hu ◽  
Jingshu Wang ◽  
Xin Zhong ◽  
Yinzhu Chen ◽  
...  
Keyword(s):  
Impedance Measurement ◽  
Transference Number ◽  
Potential Scattering ◽  
Charge Carriers ◽  
Ion Diffusion ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Transportation Process ◽  
Electron Transportation ◽  
Electrical And Dielectric Properties

Calcium fluoride (CaF2) nanoparticles with various terbium (Tb) doping concentrations were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and alternating current (AC) impedance measurement. The original shape and structure of CaF2 nanoparticles were retained after doping. In all the samples, the dominant charge carriers were electrons, and the F− ion transference number increased with increasing Tb concentration. The defects in the grain region considerably contributed to the electron transportation process. When the Tb concentration was less than 3%, the effect of the ionic radius variation dominated and led to the diffusion of the F− ions and facilitated electron transportation. When the Tb concentration was greater than 3%, the increasing deformation potential scattering dominated, impeding F− ion diffusion and electron transportation. The substitution of Ca2+ by Tb3+ enables the electron and ion hopping in CaF2 nanocrystals, resulting in increased permittivity.

scholarly journals An Efficient and Novel Ammonia Sensor Based on Polypyrrole/Tin Oxide/MWCNT Nanocomposite

2020 ◽  
Vol 32 (6) ◽  
pp. 1505-1510
Author(s):  
Ahmad Husain ◽  
Mohd Urooj Shariq ◽  
Anees Ahmad
Keyword(s):  
Electron Microscopy ◽  
Tin Oxide ◽  
Charge Carriers ◽  
Morphological Properties ◽  
X Ray Diffraction ◽  
Ammonia Sensing ◽  
Transmission Electron ◽  
Ft Ir ◽  
Ft Ir Spectroscopy

In present study, the synthesis and characterization of a novel polypyrrole (PPy)/tin oxide (SnO2)/MWCNT nanocomposite along with pristine polypyrrole is reported. These materials have been studied for their structural and morphological properties by FT-IR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. PPy/SnO2/MWCNT nanocomposite has been converted into a pellet-shaped sensor, and its ammonia sensing studies were carried out by calculating the variation in the DC electrical conductivity at different concentration of ammonia ranging from 10 to 1500 ppm. The sensing response of the sensor was determined at 1500, 1000, 500, 200, 100 and 10 ppm and found to be 70.4, 66.1, 62.2, 55.4, 50.8 and 39.7%, respectively The sensor showed a complete reversibility at lower concentrations along with excellent selectivity and stability. Finally, a sensing mechanism was also proposed involving polarons (charge carriers) of polypyrrole and lone pairs of ammonia molecules

Photocurrent in a hybrid system of 1-thioglycerol and HgTe quantum dots

2003 ◽  
Vol 789 ◽  
Author(s):  
Hyunsuk Kim ◽  
Kyoungah Cho ◽  
Byungdon Min ◽  
Jong Soo Lee ◽  
Man Young Sung ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Hybrid System ◽  
Wavelength Dependence ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
Electron Hole ◽  
Free Carriers ◽  
Transmission Electron ◽  
Colloidal Method ◽  
First Time

ABSTRACTPhotocurrent mechanism in a hybrid system of 1-thioglycerol and HgTe quantum dots(QDs) was studied for the first time in the intra-red (IR) range. 1-thioglycerol-capped HgTe QDs were prepared using colloidal method in aqueous solution; the synthesis and size of the HgTe QDs were examined by x-ray diffraction, Raman scattering, and high-resolution transmission electron microscopy. Absorption and photoluminescence spectra of the capped HgTe QDs revealed the strong excitonic peaks in the range from 900 to 1100nm, because of their widened band gap due to the shrinkage of their sizes to about 3 nm. The wavelength dependence of the photocurrent for the hybred system of the 1-thioglycerol and HgTe QDs was very close to that of the absorption spectrum, indicating that charge carriers photoexcited in the HgTe QDs give direct contribution to the photocurrent in the medium of 1-thioglycerol. In this hybrid system, the photo-excited electrons in the HgTe QDs are strongly confined, but the photo-excited holes act as free carriers. Hence, in the photocurrent mechanism of the this hybrid system, only holes among electron-hole pairs created by incident photons in the HgTe QDs are transferred to 1-thioglycerol surrounding HgTe QDs and contribute photocurrent flowing in the medium of 1-thioglycerol.

Bi2Sr2M'2M”O11.5 [(M' = Nb, Ta) and (M” = Al, Ga)], Synthesis and Characterization of Oxygen-Deficient Aurivillius Phases

1994 ◽  
Vol 369 ◽  
Author(s):  
Kurt R. Kendall ◽  
Carlos J. Navas ◽  
Hans-Conrad Zur Loye
Keyword(s):  
Ionic Conductivities ◽  
Transference Number ◽  
Atmospheric Conditions ◽  
New Materials ◽  
Ionic Conductors ◽  
X Ray Diffraction ◽  
Aurivillius Phases ◽  
Arrhenius Plots ◽  
Transmission Electron

AbstractOxygen-deficient layered bismuth oxides, Bi2Sr2M'2M”O11.5 [(M' = Nb, Ta) and (M” = Al, Ga)] were synthesized. Powder X-ray diffraction and transmission electron microscopy were usedto characterize the new materials' structures. The ionic conductivity was measuredusing impedance spectroscopy which indicated the existence of multiple conductive states in the new oxygen-deficient materials. Arrhenius plots of the conductivity showed discontinuities which were attributed to transitions between different conductive states. At 800ºC, Bi2Sr2Nb2GaO11.5 and Bi2Sr2Nb2A1O1.5, have ionic conductivities of 2.0×10−2 S/cm and 1.2×10−2 S/cm, respectively. Differential thermal analysis showed phase transitions in the oxygen-deficient materials. These transitionsoccurred at temperatures similar to those at which discontinuities were observed in the Arrhenius plots of the conductivity and are attributed to oxygen vacancy order/disorder transitions. The transference number was calculated for some of the samples by measuring both the EMF and the conductivity as a function of oxygen partial pressure. Under atmospheric conditions the new materials are predominantly ionic conductors.

Synthesis of Bi0.5Sb1.5Te3/Graphene Composite Powders

2013 ◽  
Vol 743-744 ◽  
pp. 83-87
Author(s):  
B.B. Liang ◽  
Y. Li ◽  
L.L. Xu ◽  
L.J. Wang ◽  
W. Jiang
Keyword(s):  
Electron Microscopy ◽  
Active Sites ◽  
Synthesis Method ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
Composite Powders ◽  
X Ray ◽  
Graphene Composite ◽  
Transmission Electron ◽  
Different Content

In this paper, Bi0.5Sb1.5Te3/graphene composite powders were prepared by hydrothermal synthesis method. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were used to characterize the morphology and structure of the composite powders. As a nanocomposite phase, graphene provided plenty of charge carriers and active sites for nucleation of Bi0.5Sb1.5Te3 grains. Bi0.5Sb1.5Te3 particles aggregated and attached to the surfaces of graphene randomly. In addition, it was found that the sizes of Bi0.5Sb1.5Te3 particles varied with different content of graphene. The formation mechanism of Bi0.5Sb1.5Te3/graphene composite powders was discussed.

scholarly journals Synthesis, Characterization and Ammonia Sensing Studies on Novel Polypyrrole/Zinc Oxide/SWCNT Nanocomposite

2020 ◽  
Vol 32 (8) ◽  
pp. 1961-1966
Author(s):  
Ahmad Husain ◽  
Mohd Urooj Shariq ◽  
Sharique Ahmad ◽  
Anees Ahmad ◽  
Faiz Mohammad
Keyword(s):  
Electron Microscopy ◽  
Zinc Oxide ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
Ammonia Sensing ◽  
Transmission Electron ◽  
Ft Ir ◽  
Very High ◽  
Ft Ir Spectroscopy

Herein, the synthesis and characterization of a novel polypyrrole (PPy)/zinc oxide (ZnO)/SWCNT nanocomposite together with pristine polypyrrole is reported. These as-prepared materials have been characterized by FT-IR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) techniques. The PPy/ ZnO/SWCNT nanocomposite is used as a pellet-shaped ammonia sensor. The sensing response is calculated in terms of variation in the DC electrical conductivity at different concentration of ammonia ranging from 50 ppm to 2000 ppm. The sensing response of the sensor is determined at 2000, 1000, 500, 400, 300, 200, 100 and 50 ppm and found to be 76.3, 60.5, 54.8, 52.6, 50.2, 48.5, 40.5 and 36.6%, respectively The sensor displays excellent reversibility along with very high selectivity and stability. Finally, a sensing mechanism is also proposed involving polarons (charge carriers) of polypyrrole and lone pairs of electrons of ammonia molecules.

The Properties and Enhanced Photocatalytic Behaviour of TiO2-RGO Nanocomposites

2014 ◽  
Vol 707 ◽  
pp. 94-97
Author(s):  
Fang Jun Wu ◽  
Wei Liu ◽  
Jia Wen Mai ◽  
Jie Long Qiu ◽  
Shu Ting Zhang ◽  
...  
Keyword(s):  
Diffuse Reflectance ◽  
Diffuse Reflectance Spectroscopy ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
Wet Chemical Method ◽  
Graphene Nanocomposites ◽  
X Ray ◽  
Transmission Electron ◽  
Production Activity ◽  
Wet Chemical

TiO2-Graphene nanocomposites were prepared by a wet chemical method and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis). The nanocomposite demonstrated nice photocatalytic activity for water reduction to produce hydrogen. The optimal graphene content was found to be 10 wt%, giving a Hydrogen-production rate of 13.2 mmol∙h-1∙g-1, which significantly exceeded the rate observed on pure TiO2. This high photocatalytic H2-production activity is due to the deposition of TiO2 nanoparticles on graphene sheets, which act as an electron acceptor to efficiently separate the photogenerated charge carriers.

Electrical conduction mechanism in films of Se80−xTe20Bix (0 ≤ x ≤ 12) glassy alloys

2019 ◽  
Vol 97 (2) ◽  
pp. 222-226 ◽  
Author(s):  
Deepika ◽  
Hukum Singh
Keyword(s):  
Electrical Conductivity ◽  
Physical Vapor Deposition ◽  
Conduction Mechanism ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
Glassy Alloys ◽  
Transmission Electron ◽  
Physical Vapor Deposition Method ◽  
Temperature Ranges ◽  
Lower Temperature

This paper reports the study of DC electrical conductivity of films of Se80−xTe20Bix (0 ≤ x ≤ 12) glasses prepared using physical vapor deposition method. The films were structurally characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM results indicate the formation of nanorods within the films. The electrical conductivity of the samples was studied using Keithley electrometer in the temperature range 303–373 K. The results show that conduction in these samples takes place via thermally assisted tunnelling and variable range hopping of charge carriers corresponding to higher and lower temperature ranges, respectively. Further, it was found that the conductivity increases with increase in Bi concentration in Se–Te system. This has been explained on the basis of chemically ordered network model. It was also found that nanorod formation improves the electrical conductivity of Se–Te–Bi system compared to bulk Se–Te–Bi system.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

A High Resolution Study of G.P. Zones in Aluminum - 4.2 at % Silver

1982 ◽  
Vol 40 ◽  
pp. 722-723 ◽  
Author(s):  
R. Gronsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Computer Simulations ◽  
Structural Characteristics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Resolution Study

The phenomenon of clustering in Al-Ag alloys has been extensively studied since the early work of Guinierl, wherein the pre-precipitation state was characterized as an assembly of spherical, ordered, silver-rich G.P. zones. Subsequent x-ray and TEM investigations yielded results in general agreement with this model. However, serious discrepancies were later revealed by the detailed x-ray diffraction - based computer simulations of Gragg and Cohen, i.e., the silver-rich clusters were instead octahedral in shape and fully disordered, atleast below 170°C. The object of the present investigation is to examine directly the structural characteristics of G.P. zones in Al-Ag by high resolution transmission electron microscopy.

Identification of calcium oxalate crystals in dried or fixed tobacco leaf

1984 ◽  
Vol 42 ◽  
pp. 288-289
Author(s):  
Vicki L. Baliga ◽  
Mary Ellen Counts
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Calcium Oxalate ◽  
Growth And Development ◽  
Polarized Light ◽  
Calcium Oxalate Crystals ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Electron

Calcium is an important element in the growth and development of plants and one form of calcium is calcium oxalate. Calcium oxalate has been found in leaf seed, stem material plant tissue culture, fungi and lichen using one or more of the following methods—polarized light microscopy (PLM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and x-ray diffraction.Two methods are presented here for qualitatively estimating calcium oxalate in dried or fixed tobacco (Nicotiana) leaf from different stalk positions using PLM. SEM, coupled with energy dispersive x-ray spectrometry (EDS), and powder x-ray diffraction were used to verify that the crystals observed in the dried leaf with PLM were calcium oxalate.

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