Search results for "Impurity"
showing 10 items of 330 documents
Using the methods of radiospectroscopy (EPR, NMR) to study the nature of the defect structure of solid solutions based on lead zirconate titanate (PZ…
2014
The nature of intrinsic and impurity point defects in lead zirconate titanate (PZT) ceramics has been explored. Using electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), and X-ray photoelectron spectroscopy (XPS) methods, several impurity sites have been identified in the materials, including the Fe 3+ -oxygen vacancy (VO) complex and Pb ions. Both of these centers are incorporated into the PZT lattice. The Fe 3+ -V paramagnetic complex serves as a sensitive probe of the local crystal field in the ceramic; the symmetry of this defect roughly correlates with PZT phase diagram as the composition is varied from PbTiO 3 to PbZrO 3 . NMR spectra 207 Pb in PbTiO 3 , PbZrO 3 ,…
Usability of Cr-Doped Alumina in Dosimetry
2019
Dosimetry is a widespread material science field dealing with detection and quantification of ionizing radiation using electronic processes in materials. One of the main aspects that determines the performance of dosimeters is the type of defects the material contains. Crystalline lattice imperfections are formed around impurity ions, which may have a smaller or larger size, or different oxidation states compared to host ions. In this study, we show what effects Cr impurities have on the luminescent properties of alumina. Porous Al 2 O 3 : Cr microceramics synthesized using the sol-gel method showed a higher thermoluminescence response than a single crystal ruby. We have found that Cr 2 O 3…
The nature of the defect structure of solid solutions based on lead zirconate titanate (PZT): Evidence from EPR and NMR
2013
The nature of intrinsic and impurity point defects in lead zirconate titanate (PZT) ceramics has been explored. Using electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) methods several impurity sites have been identified in the materials, including Fe3+-oxygen vacancy (VO) complex and Pb ions. Both of these centers are incorporated into the PZT lattice. The Fe3+-VO paramagnetic complex serves as a sensitive probe of the local crystalline field in the ceramic; the symmetry of this defect is roughly correlated with PZT phase diagram as composition is varied from PbTiO3 to PbZrO3. NMR spectra 207Pb in PbTiO3, PbZrO3 and PZT with iron content from 0 to 0.4 mol % showed t…
Atomic layer deposition and characterization of biocompatible hydroxyapatite thin films
2009
Abstract Atomic layer deposition (ALD) was used to produce hydroxyapatite from Ca(thd) 2 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionato) and (CH 3 O) 3 PO onto Si(100) and Corning (0211). Film crystallinity, stoichiometry, possible impurities and surface morphology were determined. The as-deposited films contained significant amounts of carbonate impurities however, annealing at moist N 2 flow reduced the carbonate content even at 400 °C. The as-deposited Ca–P–O films were amorphous but rapid thermal annealing promoted the formation of the hydroxyapatite phase. Mouse MC 3T3-E1 cells were used for the cell culture experiments. According to the bioactivity studies cell proliferation was enhanc…
Density functional study of gold atoms and clusters on a graphite (0001) surface with defects
2006
Adsorption of gold atoms and clusters $(N=6)$ on a graphite (0001) surface with defects has been studied using density functional theory. In addition to perfect graphite (0001), three types of surface defects have been considered: a surface vacancy (hole), a pyridinelike defect comprising three grouped nitrogen atoms, and a substitutional doping by N or B. Results for Au and ${\mathrm{Au}}_{6}$ indicate that the surface vacancy can form chemical bonds with Au as the three nearby carbons align their dangling bonds towards the gold particle (binding energy 2.4--$2.6\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$). A similar chemically saturated holelike construction with three pyridinic N atoms resul…
Comparative Acoustic and Contact Studies of Elasticity of Ferroelectric LixNa1 - xTa0.1Nb0.9O3Solid Solutions at Nanometer Spatial Resolution
2009
Comparative acoustic and contact studies of elastic properties of the Li x Na 1−x Ta 0.1 Nb 0.9 O 3 (x = 0.015–0.135) ferroelectric solid solution ceramics are reported. A good agreement is obtained between the values of elastic modules determined by acoustic and contact methods at nano-scale spatial resolution.
Application of AC and DC magnetic field for surface wave excitation to enhance mass transfer
2020
Abstract Refining the metallic melts and removal of contaminants from the free surface may be sped up by increasing the surface area of mass exchange interface. It is relevant to both the case of volatile impurity evaporation in a vacuum as well as the case of chemical reactions when the continuous crust of reaction products should be interrupted. Previously proposed low-frequency AC magnetic field excitation of intense surface waves is limited by skin-effect. The induced sign-alternating forcing at high dimensionless frequency values becomes dominantly pulsing at considerably higher than unity values, delivering time-averaged stirring without intense surface waves. Superimposing DC magneti…
Optical properties of an exciton bound to an ionized impurity in ZnO/SiO2 quantum dots
2015
Abstract The energy of the ground and the excited states for the exciton and the binding energy of the acceptor–donor exciton complexes ( A − , X ) and ( D + , X ) as a function of the radius for an impurity position located in the center in the spherical ZnO quantum dots (QDs) embedded in a SiO2 matrix are calculated using the effective mass approximation under the diagonalzation matrix technique, including a three-dimensional confinement of carrier in the QD and assuming a finite depth. Numerical results show that the binding energy of the acceptor–donor exciton complexes is very sensitive to the quantum dot size. These results could be particularly helpful since they are closely related …
Optical properties of acceptor–exciton complexes in ZnO/SiO2 quantum dots
2011
Abstract The binding energy E b of the acceptor–exciton complex (A − ,X) as a function of the radius (or of the impurity position of the acceptor) and the normalized oscillator strength of (A − ,X) in spherical ZnO quantum dots (QDs) embedded in a SiO 2 matrix are calculated using the effective-mass approximation under the diagonalzation matrix technique, including a three-dimensional confinement of the carrier in the QD and assuming a finite depth. Numerical results show that the binding energy of the acceptor–exciton complexes is particularly robust when the impurity position of the acceptor is in the center of the ZnO QDs. It has been clearly shown from our calculations that these physic…
Detection of magnetic thin film impurity phases using nitrogen vacancy centers in diamond crystal
2019
We demonstrate the possibility to detect magnetic impurity phases in thin films using magnetic field imaging technique based on a layer of nitrogen-vacancy centers in the diamond lattice. We demonstrate results of magnetic field distributions created by impurity phases as well as mechanical defects on the thin film surface.