scholarly journals Парамагнитные антисайт Mn-дефекты в нанокерамике алюмомагниевой шпинели

2020 ◽  
Vol 62 (1) ◽  
pp. 94
Author(s):  
А.Ф. Зацепин ◽  
А.Н. Киряков ◽  
Д.Р. Байтимиров ◽  
Т.В. Дьячкова ◽  
А.П. Тютюнник ◽  
...  
Keyword(s):  
Single Crystal ◽  
Structure Constant ◽  
Charge Compensation ◽  
Lattice Parameter ◽  
Paramagnetic Centers ◽  
Initial State ◽  
Spectral Parameters ◽  
Hyperfine Structure Constant ◽  
F Center ◽  
Reference Samples

The influence of structural and dimensional factors on the formation of intrinsic and impurity paramagnetic centers in nanoceramics of aluminum-magnesium spinel is studied. The studied samples (with a grain size of 30 nm) were obtained by thermobaric synthesis. Microcrystalline ceramics and a MgAl2O4 single crystal were used as standards. The single crystal and microceramics contain characteristic Mn2+ paramagnetic centers (hyperfine structure constant (HFS) A = 82 G). In the studied nanoceramic samples in the initial state, both impurity Mn2+ and intrinsic F+ centers are detected. In contrast to nanoceramics, in reference samples centers of the F+ type appear only after irradiation with 130 keV by accelerated electrons. The parameters of the Mn2+ centers in nanoceramics differ significantly from those in microceramics and single crystals. For the Mn2+ center in nanoceramics, the EPR signal is characterized by two anomalous HFS constants (A1 = 91.21 G, A2 = 87.83 G) caused by two varieties of octahedrally coordinated manganese ions (anti-site defects [Mn2+]Al3+). The specific features of the spectral parameters of manganese centers correlate with a decrease in the lattice parameter of MgAl2O4 in the nanostructured state. The observed effects are interpreted based on the proposed charge compensation scheme of [Mn2+]Al3+ with an aluminum anti-site defect and an F+ center.

Microstructural characterization of YBaCuO Films on LaAlO3 substrates

1989 ◽  
Vol 47 ◽  
pp. 180-181
Author(s):  
E. L. Hall ◽  
A. Mogro-Campero ◽  
N. Lewis ◽  
L. G. Turner
Keyword(s):  
Dielectric Constant ◽  
Single Crystal ◽  
Film Growth ◽  
Microstructural Characterization ◽  
Lattice Parameter ◽  
Film Plane ◽  
Substrate Material ◽  
High Loss ◽  
Amorphous Substrates ◽  
High Dielectric

There have been a large number of recent studies of the growth of Y-Ba-Cu-O thin films, and these studies have employed a variety of substrates and growth techniques. To date, the highest values of Tc and Jc have been found for films grown by sputtering or coevaporation on single-crystal SrTiO3 substrates, which produces a uniaxially-aligned film with the YBa2Cu3Ox c-axis normal to the film plane. Multilayer growth of films on the same substrate produces a triaxially-aligned film (regions of the film have their c-axis parallel to each of the three substrate <100> directions) with lower values of Jc. Growth of films on a variety of other polycrystalline or amorphous substrates produces randomly-oriented polycrystalline films with low Jc. Although single-crystal SrTiO3 thus produces the best results, this substrate material has a number of undesireable characteristics relative to electronic applications, including very high dielectric constant and a high loss tangent at microwave frequencies. Recently, Simon et al. have shown that LaAlO3 could be used as a substrate for YBaCuO film growth. This substrate is essentially a cubic perovskite with a lattice parameter of 0.3792nm (it has a slight rhombohedral distortion at room temperature) and this material exhibits much lower dielectric constant and microwave loss tangents than SrTiO3. It is also interesting from a film growth standpoint since it has a slightly smaller lattice parameter than YBa2Cu3Ox (a=0.382nm, b=c/3=0.389nm), while SrTiO3 is slightly larger (a=0.3905nm).

scholarly journals Growth of sillenite Bi12FeO20 single crystals: structural, thermal, optical, photocatalytic features and first principle calculations

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Durga Sankar Vavilapalli ◽  
Ambrose A. Melvin ◽  
F. Bellarmine ◽  
Ramanjaneyulu Mannam ◽  
Srihari Velaga ◽  
...  
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Photoelectron Spectroscopy ◽  
Diffraction Method ◽  
Lattice Parameter ◽  
First Principle ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Principle Calculations ◽  
Photodegradation Efficiency

AbstractIdeal sillenite type Bi12FeO20 (BFO) micron sized single crystals have been successfully grown via inexpensive hydrothermal method. The refined single crystal X-ray diffraction data reveals cubic Bi12FeO20 structure with single crystal parameters. Occurrence of rare Fe4+ state is identified via X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The lattice parameter (a) and corresponding molar volume (Vm) of Bi12FeO20 have been measured in the temperature range of 30–700 °C by the X-ray diffraction method. The thermal expansion coefficient (α) 3.93 × 10–5 K−1 was calculated from the measured values of the parameters. Electronic structure and density of states are investigated by first principle calculations. Photoelectrochemical measurements on single crystals with bandgap of 2 eV reveal significant photo response. The photoactivity of as grown crystals were further investigated by degrading organic effluents such as Methylene blue (MB) and Congo red (CR) under natural sunlight. BFO showed photodegradation efficiency about 74.23% and 32.10% for degrading MB and CR respectively. Interesting morphology and microstructure of pointed spearhead like BFO crystals provide a new insight in designing and synthesizing multifunctional single crystals.

Single Crystal Zirconia Thin Films from Liquid Precursors

1989 ◽  
Vol 155 ◽  
Author(s):  
K. T. Miller ◽  
F. F. Lange
Keyword(s):  
Single Crystal ◽  
Lattice Mismatch ◽  
Lattice Parameter ◽  
Precursor Film ◽  
Yttrium Nitrate ◽  
X Ray Diffraction ◽  
Zirconium Acetate ◽  
Liquid Precursors ◽  
Crystal Film ◽  
Crystal Films

ABSTRACTEpitaxial, single-crystal films of ZrO2 (Y2O3) were formed on (100) oriented single crystal substrates of ZrO2 (9.5 mol% Y2O3) using water-based solutions of zirconium acetate and yttrium nitrate as a precursor. Film compostions of ZrO2 (0 - 40 mol% Y2O3) were examined; since the lattice parameter of ZrO2 (Y2O3) increases with yttria content, the lattice mismatch was systematically varied to a maximum of 1.5%. Precursor films were deposited by spin coating, pyrolyzed, and held for 1 hour at 900°C, 1000°C, and 1100°C. X-ray diffraction showed that a strongly oriented film had developed after pyrolysis of the precursor. In addition, all samples, except those treated at 1100°C containing 6 – 15 mol% Y2O3, gave (111) peaks, indicating film polycrystallinity. Electron back-scattering patterns showed that epitaxial single crystals were formed at 1100°C for films containing 3 – 20 mol% Y2O3. Scanning electron microscopy showed that the epitaxial films had a porous structure. These results indicate that the epitaxy is a two-stage process: oriented nucleation upon pyrolysis, followed, for low mismatches, by subsequent consolidation into a single-crystal film above 1000°C.

THERMAL, DIELECTRIC STUDIES ON PURE AND AMINO ACID (L-GLUTAMIC ACID, L-HISTIDINE, L-VALINE) DOPED POTASSIUM DIHYDROGEN PHOSPHATE SINGLE CRYSTALS

2007 ◽  
Vol 16 (02) ◽  
pp. 255-268 ◽  
Author(s):  
P. KUMARESAN ◽  
S. MOORTHY BABU ◽  
P. M. ANBARASAN
Keyword(s):  
Amino Acids ◽  
Glutamic Acid ◽  
Potassium Dihydrogen Phosphate ◽  
Lattice Parameter ◽  
Dihydrogen Phosphate ◽  
Dielectric Studies ◽  
Slow Cooling ◽  
Spectral Parameters ◽  
Potassium Dihydrogen ◽  
Good Thermal Stability

Amino acids (L-Glutamic acid, L-Histidine, L-Valine) doped potassium dihydrogen phosphate crystals were grown by the solution growth technique. Slow cooling as well as slow evaporation methods were employed to grow these crystals. The concentration of dopants in the mother solution was varied from 0.1 mole % to 10 mole %. The solubility data for all dopant concentrations were determined. The variation in pH and the corresponding habit modification of the grown crystals were characterized with UV - VIS, FT-IR and SHG trace elements, and dielectric studies reveal slight distortion of lattice parameter for the heavily doped KDP crystals. TGA-DTA studies reveal good thermal stability. The dopants increase the hardness value of the material, which also depends on the concentration of the dopants. Amino acids doping improved the NLO properties. The detailed results on the spectral parameters, habit modifications and constant values will be presented.

Pressure Shifts in the Hyperfine Structure Constant of Potassium

1960 ◽  
Vol 119 (6) ◽  
pp. 1946-1947 ◽  
Author(s):  
Arnold L. Bloom ◽  
John B. Carr
Keyword(s):  
Hyperfine Structure ◽  
Structure Constant ◽  
Hyperfine Structure Constant

Tem Observations of Interfacial Defects in Mocvd GaAs on Single Crystal Ge Substrates

1998 ◽  
Vol 4 (S2) ◽  
pp. 626-627
Author(s):  
K.M. Jones ◽  
M.M. Al-Jassim ◽  
J.M. Olson
Keyword(s):  
Thermal Expansion ◽  
Solar Cell ◽  
Physical Properties ◽  
Single Crystal ◽  
High Efficiency ◽  
Lattice Parameter ◽  
High Quality ◽  
Stages Of Growth ◽  
Interfacial Defects ◽  
Microstructural Defects

The growth of high quality GaAs layers on single crystal Ge substrates has attracted a great deal of interest in recent years. Currently under development at NREL is the GaAs/GalnP-on-Ge high efficiency multi-junction solar cell. Unlike other heteroepitaxial systems such as GaAs-on-Si, physical properties such as the lattice parameter and thermal expansion coefficient of the Ge and GaAs are much closer. Further, Ge has a bandgap of 0.7 eV that makes it a suitable bottom cell in a multi-junction stack. However, the growth of GaAs on Ge is not a straightforward process, and little is known about the Ge surface and the nucleation of GaAs on Ge in the MOCVD environment. In this study, TEM results show that a number microstructural defects are associated with the Ge/GaAs interface and the initial stages of growth.

Single-crystal Fe-bearing sphalerite: synthesis, lattice parameter, thermal expansion coefficient and microhardness

2016 ◽  
Vol 44 (4) ◽  
pp. 287-296 ◽  
Author(s):  
Dmitriy A. Chareev ◽  
Valentin O. Osadchii ◽  
Andrey A. Shiryaev ◽  
Alexey N. Nekrasov ◽  
Anatolii V. Koshelev ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Single Crystal ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Lattice Parameter

Quantification of mobilized copper(II) levels in micronized copper-treated wood by electron paramagnetic resonance (EPR) spectroscopy

Holzforschung ◽  
2013 ◽  
Vol 67 (7) ◽  
pp. 815-823 ◽  
Author(s):  
Wei Xue ◽  
Pierre Kennepohl ◽  
John N.R. Ruddick
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Epr Spectroscopy ◽  
Treated Wood ◽  
Spectral Parameters ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Acid Reaction ◽  
Epr Signal ◽  
Electron Paramagnetic ◽  
Reference Samples

Abstract Sapwood sawdust from southern pine was treated with micronized copper (MC) under various conditions and the mobilized copper(II) (Cumob) concentrations were determined in the treated wood by electron paramagnetic resonance (EPR) spectroscopy. The spectral parameters for the copper sulfate (CuSO4)-treated sapwood and those of the MC-treated sapwood were very similar. A linear correlation was found between the intensities of copper (Cu) EPR spectra and those of Cu energy-dispersive X-ray fluorescence spectroscopy in a series of CuSO4-treated sapwood reference samples. Thus, the EPR signal intensities could be reliably correlated to the mass of reacted Cu present using this calibration curve. The amount of the Cumob in sawdust treated by MC suspensions increased during the first 2–3 days after the initial treatment and then reached a maximum during the 7-day monitoring period. In the case of the treatment with MC alone or MC azole, an increased MC concentration led to an elevated amount of Cu (to a maximum of ∼0.23% Cu) solubilized by the sapwood. If the wood was treated with MC quat, the Cumob initially increased, but at higher concentrations the Cumob content decreased, due to the interference by the quat cobiocide on the acid reaction between the wood and the basic Cu carbonate. An examination of commercially-treated wood confirmed the laboratory observations.

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