scholarly journals Crystal Defects and Cation Redistribution Study on Nanocrystalline Cobalt-Ferri-Chromites by Positron Annihilation Spectroscopy

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Kunal B. Modi ◽  
Nimish H. Vasoya ◽  
Vinay K. Lakhani ◽  
Tushar K. Pathak ◽  
P. M. G. Nambissan
Keyword(s):  
Spinel Ferrite ◽  
Positron Annihilation Spectroscopy ◽  
Crystal Defects ◽  
X Ray Diffraction ◽  
Lattice Contraction ◽  
General Chemical ◽  
Coprecipitation Technique ◽  
Normal Spinel ◽  
Cation Redistribution ◽  
Subsequent Stabilization

Positron lifetime and Doppler broadening measurements were carried out on nanocrystalline (grain size ~60–65 nm) samples of the Cr3+-substituted cobalt ferrite system with general chemical formula CoCrxFe2−xO4 (x=0.0−2.0) synthesized by the coprecipitation technique. The results indicated selective trapping of positrons in large vacancy clusters initially at the tetrahedral (A-) sites and then with Cr3+-substitution up to concentration (x)=0.7, at the octahedral (B-) sites. The results are consistent with the cation distribution determined from X-ray diffraction line intensity calculations, which indicated partial inversion of the inverse spinel ferrite, subsequent stabilization over a range of substitution (x=0.7 to 1.7), and finally the full inversion to the normal spinel chromite (CoCr2O4, x=2.0). In the intermediate range of substitution, lattice contraction prevented a fraction of Co2+ ions released from the (B-) sites from entering the tetrahedral sites, and these vacancies at the (A-) sites trapped positrons. Although the samples were composed of nanocrystalline grains, only an insignificant fraction of positrons were diffused and annihilated at the grain surfaces, since the grain sizes and the thermal diffusion length of positrons nearly overlapped.

scholarly journals Multifunctional Hierarchically Architectured ZnO for Luminescence, Photocatalytic, Electrocatalytic, and Energy Storage Applications

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1025
Author(s):  
V. P. Singh ◽  
Mirgender Kumar ◽  
B. Purusottam Reddy ◽  
Sunny ◽  
R. K. Gangwar ◽  
...  
Keyword(s):  
Energy Storage ◽  
Waste Water Treatment ◽  
Positron Annihilation Spectroscopy ◽  
X Ray Diffraction ◽  
Supercapacitor Electrode ◽  
Intermediate Phases ◽  
Coprecipitation Technique ◽  
Energy Storage Applications ◽  
White Luminescence ◽  
Highly Porous

Hierarchically ZnO nanoarchitecture synthesized through coprecipitation technique. Growth process has been analyzed by varying pH from 5.5 to 13 along with post heat treatment process through the observation of surface morphology from 2D plates, triangular, hexagonal rods, needles, and finally to hierarchical. X-ray diffraction (XRD) reveals many intermediate phases along with ZnO which has been eliminated through the proper pH and temperature. The native defects have been discussed by using Raman and positron annihilation spectroscopy. Further, multifunctional properties of synthesized material have been discussed by candle-like warm white luminescence, photocatalysis, electrocatalysis and energy storage applications. Specially hierarchically nanoarchitecture found suitable for warm white lighting along with effective for waste water treatment by visible light. The highly porous property of the same material made itself appropriate for effective oxygen evaluation reaction and hydrogen evolution reaction together with reduced overpotential and Tafel slope. The application for supercapacitor electrode (~780 F/g) also has been revealed which opened new dimension for hierarchical ZnO.

Effects of Film Interfaces on the Properties of Poly-Si Grown by The Metal-Induced Technique for Solar Cell Applications

2003 ◽  
Vol 796 ◽  
Author(s):  
Chunhai Ji ◽  
Wayne A. Anderson
Keyword(s):  
Seed Layer ◽  
Lattice Mismatch ◽  
Xrd Analysis ◽  
Crystal Defects ◽  
Photon Absorption ◽  
X Ray Diffraction ◽  
Lattice Match ◽  
Silicide Layer ◽  
Layer Sample ◽  
The One

ABSTRACTIn the metal-induced growth (MIG) process, the poly-Si layer hetero-epitaxially grows from a thin silicide layer, formed by reaction of a metal seed-layer and sputtered silicon, due to an extremely close lattice match between silicon and the metal silicide. The produced poly-Si has shown a promising device quality for photovoltaic applications. Recent results show that the interface of the silicide and poly-Si has a significant effect on the properties of the poly-Si which works as an active layer for photon absorption. In the study of the MIG process, two metals were used as a seed-layer, i.e. Ni and Co. Although CoSi2has a larger lattice mismatch with Si (1.2%) than does NiSi2(0.4%), the poly-Si growing from Co has a smoother interface between the poly-Si and silicide, while the one for the Ni seed-layer samples is rather rough. Backscattered XSEM shows that the Ni-contained phase extended into the Si layer by forming long spikes. This might cause crystal defects in the Si layer. The Auger depth profile also showed that the Ni atoms diffuse into the Si layer much more than does the Co. This kind of difference in interface structure causes the different properties of the poly-Si layer. X-ray diffraction (XRD) analysis on the Si layer showed that the Co seed-layer sample had a predominant growth orientation of (220) and the FWHM of 0.2°. The Ni seed-layer samples grew mainly in both <111> and <220> direction, with FWHM of 0.3° and 0.4°, respectively. By comparison, the poly-Si from the Co seed-layer had a higher carrier lifetime of 0.458μs compared to 0.305μs from Ni.

Effect of Ce3+ Ions Doped NiFe2O4 Magnetic Nanoparticles on Photocatalytic Degradation of Rhodamine B and Antibacterial Activities

2021 ◽  
Vol 21 (11) ◽  
pp. 5784-5793
Author(s):  
K. Geetha ◽  
R. Udhayakumar
Keyword(s):  
Photocatalytic Degradation ◽  
Rhodamine B ◽  
Spinel Ferrite ◽  
Magnetic Hysteresis ◽  
Aloe Vera ◽  
Antibacterial Activities ◽  
X Ray Diffraction ◽  
X Ray ◽  
E Coli ◽  
Ferrite Structure

In this study, spinel NiCexFe2–XO4 (x = 0.0 - 0.5) nanoparticles (NPs) was synthesized by microwave combustion technique (MCT) utilizing the fuel of Aloe vera plant extract. The establishment of spinel cubic crystal structure was ensured by powder X-ray diffraction (PXRD) technique. The particles like nanostructured morphology were confirmed by high-resolution scanning electron microscope (HRSEM). Energy dispersive X-ray (EDX) studies confirmed the formation of spinel ferrite structure and ensured that no other elements were present. Magnetic parameters such as remanant magnetisation (Mr), coercivity (He) and saturation magnetization (Ms) were calculated from the magnetic hysteresis (M-H) loops, which exhibited ferromagnetic behaviour. The photocatalytic behavior was investigated by visible light treatment for the photocatalytic degradation (PCD) of rhodamine B (Rh-B) dye and the sample NiCe0.3Fe1.7O4 exhibits higher PCD efficiency (93.88%) than other compositions. The antibacterial activities of gram-positive S. aureus, B. subtilis, gramnegative K. pneumonia and E. coli have been investigated using undoped and Ce3+ substituted NiFe2O4 NPs and observed higher activity, which indicated that, they can be used in the bio-medical applications.

scholarly journals Ba5(IO6)2: crystal structure evolution from room temperature to 80 K

2021 ◽  
Vol 77 (6) ◽  
pp. 634-637
Author(s):  
David Wenhua Bi ◽  
Priya Ranjan Baral ◽  
Arnaud Magrez
Keyword(s):  
Crystal Structure ◽  
Room Temperature ◽  
Structural Transition ◽  
Rietveld Method ◽  
Structural Parameters ◽  
Structure Evolution ◽  
X Ray Diffraction ◽  
Lattice Contraction ◽  
Interatomic Distances ◽  
Crystallographic Axes

The crystal structure of Ba5(IO6)2, pentabarium bis(orthoperiodate), has been re-investigated at room temperature based on single-crystal X-ray diffraction data. In comparison with a previous crystal structure determination by the Rietveld method, an improved precision of the structural parameters was achieved. Additionally, low-temperature measurements allowed the crystal structure evolution to be studied down to 80 K. No evidence of structural transition was found even at the lowest temperature. Upon cooling, the lattice contraction is more pronounced along the b axis. This contraction is found to be inhomogeneous along different crystallographic axes. The interatomic distances between different Ba atoms reduce drastically with lowering temperature, resulting in a closer packing around the IO6 octahedra, which remain largely unaffected.

scholarly journals Imperfect Crystals and Dynamical X-ray Diffraction in the Complex Reflectance Plane

1991 ◽  
Vol 44 (6) ◽  
pp. 693 ◽  
Author(s):  
TJ Davis
Keyword(s):  
Stochastic Model ◽  
Parameter Space ◽  
Langevin Equation ◽  
Planck Equation ◽  
Theoretical Framework ◽  
Crystal Defects ◽  
X Rays ◽  
X Ray Diffraction ◽  
Dynamical Diffraction ◽  
X Ray

A theoretical framework is developed to describe the dynamical diffraction of X-rays in perfect and imperfect crystals. The propagation of the X-ray beam inside the crystal is described by the evolution of a set of trajectories in the complex reflectance plane. The trajectory path is determined from a form of the Takagi-Taupin equations and leads naturally to simple forms for the crystal reflectivity for perfect crystals. A stochastic model for the effects of crystal defects is developed in terms of the Langevin equation which leads to a description of diffraction from imperfect crystals as the evolution of densities in a parameter space, described by a Fokker-Planck equation.

Changes in the Spectral Characteristics of Aluminum Films Deposited under Assisting Argon Ion Beam

2015 ◽  
Vol 1084 ◽  
pp. 11-15
Author(s):  
Sergey P. Umnov ◽  
Oleg Kh. Asainov ◽  
Svetlana N. Popova ◽  
Aleksey N. Lemachko
Keyword(s):  
Magnetron Sputtering ◽  
Ion Beam ◽  
Spectral Characteristics ◽  
Crystal Defects ◽  
X Ray Diffraction ◽  
Aluminum Films ◽  
X Ray ◽  
Ion Assistance ◽  
Argon Ion ◽  
Uv Range

High-reflectance aluminum films are widely used in applied optics. As part of this work, we deposited aluminum films on glass substrates by magnetron sputtering using argon ion beam assistance. The reflectivity of the films obtained was measured on the SF-256 spectrophotometer. The microstructure and topology of the films were examined with a transmission electron microscope (TEM), X-ray diffraction (XRD) and atomic force microscope (AFM). The studies have shown that the aluminum films deposited with ion assistance have higher reflectance in the UV range than the films formed by magnetron sputtering alone. The results of TEM and AFM measurements show that the geometric factor (crystallite size, surface roughness) is not the reason for the increase of reflectivity. X-ray diffraction analyses have shown a significant increase in microstress in the aluminum films deposited with ion assistance, which is caused by an increase in the defect density of the vacancy-type crystal structure. The results have shown that the increase in the density of crystal defects leads to an increase in reflectance in the UV range.

Hydrogen Interaction with Defects in ZnO

2012 ◽  
Vol 733 ◽  
pp. 228-231 ◽  
Author(s):  
František Lukáč ◽  
Jakub Čížek ◽  
Marián Vlček ◽  
Ivan Procházka ◽  
Martin Vlach ◽  
...  
Keyword(s):  
Subsurface Layer ◽  
Positron Annihilation Spectroscopy ◽  
Nuclear Reaction Analysis ◽  
X Ray Diffraction ◽  
High Concentration ◽  
X Ray ◽  
Low Concentrations ◽  
Hydrogen Interaction ◽  
Induced Stresses ◽  
Zno Crystal

In the present work hydrothermally grown ZnO single crystals were electrochemically charged with hydrogen. The influence of hydrogen on ZnO microstructure was investigated by positron annihilation spectroscopy (PAS) combined with X-ray diffraction (XRD) using synchrotron radiation. Hydrogen concentration in the samples was determined by nuclear reaction analysis (NRA). It was found that a high concentration of hydrogen can be introduced into ZnO by electrochemical loading. At low concentrations, absorbed hydrogen causes elastic volume expansion of ZnO crystal. At higher concentration, hydrogen-induced stresses exceed the yield stress in ZnO and plastic deformation of the crystal takes place leading to formation of a defected subsurface layer in the crystals.

Three-dimensional X-ray diffraction imaging of process-induced dislocation loops in silicon

2011 ◽  
Vol 44 (3) ◽  
pp. 526-531 ◽  
Author(s):  
David Allen ◽  
Jochen Wittge ◽  
Jennifer Stopford ◽  
Andreas Danilewsky ◽  
Patrick McNally
Keyword(s):  
Semiconductor Industry ◽  
Three Dimensional ◽  
Crystal Defects ◽  
Three Dimensions ◽  
Dimensional Structure ◽  
Dislocation Loops ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Imaging ◽  
Relationship Of

In the semiconductor industry, wafer handling introduces micro-cracks at the wafer edge and the causal relationship of these cracks to wafer breakage is a difficult task. By way of understanding the wafer breakage process, a series of nano-indents were introduced both into 20 × 20 mm (100) wafer pieces and into whole wafers as a means of introducing controlled strain. Visualization of the three-dimensional structure of crystal defects has been demonstrated. The silicon samples were then treated by various thermal anneal processes to initiate the formation of dislocation loops around the indents. This article reports the three-dimensional X-ray diffraction imaging and visualization of the structure of these dislocations. A series of X-ray section topographs of both the indents and the dislocation loops were taken at the ANKA Synchrotron, Karlsruhe, Germany. The topographs were recorded on a CCD system combined with a high-resolution scintillator crystal and were measured by repeated cycles of exposure and sample translation along a direction perpendicular to the beam. The resulting images were then rendered into three dimensions utilizing open-source three-dimensional medical tomography algorithms that show the dislocation loops formed. Furthermore this technique allows for the production of a video (avi) file showing the rotation of the rendered topographs around any defined axis. The software also has the capability of splitting the image along a segmentation line and viewing the internal structure of the strain fields.

scholarly journals Size Effects on Magnetic Properties ofNi0.5Zn0.5Fe2O4Prepared by Sol-Gel Method

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Min Zhang ◽  
Zhenfa Zi ◽  
Qiangchun Liu ◽  
Peng Zhang ◽  
Xianwu Tang ◽  
...  
Keyword(s):  
Particle Size ◽  
Magnetic Measurements ◽  
Sol Gel ◽  
Domain Wall Motion ◽  
Blocking Temperature ◽  
Particle Sizes ◽  
X Ray Diffraction ◽  
Gel Method ◽  
Sol Gel Method ◽  
Cation Redistribution

Ni0.5Zn0.5Fe2O4particles with different particle sizes have been synthesized by sol-gel method. X-ray diffraction results show that all the samples are pure cubic spinel structure with their sizes ranging from 9 to 96 nm. The lattice constant significantly decreases with further increasing annealing temperature. The magnetic measurements show superparamagnetic nature below the particle size of 30 nm, while others show ferrimagnetic nature above the corresponding blocking temperature. The blocking temperature increases with the increase in particle size, which can be explained by Stoner-Wohlfarth theory. The saturation magnetization increases as the particle size increases, which can be explained by the cation redistribution on tetrahedral A and octahedral B sites and the domain wall motion. The variation of coercivity as a function of particle size is based on the domain structure.

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