scholarly journals Blackbody emission from CaF2 and ZrO2 nanosized dielectric particles doped with Er3+ ions

RSC Advances ◽  
2020 ◽  
Vol 10 (44) ◽  
pp. 26288-26297 ◽  
Author(s):  
P. A. Ryabochkina ◽  
S. A. Khrushchalina ◽  
I. A. Yurlov ◽  
A. V. Egorysheva ◽  
A. V. Atanova ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Band Gap ◽  
Laser Excitation ◽  
Thermal Emission ◽  
Intense Laser ◽  
Key Factors ◽  
Structure Defects ◽  
Dielectric Particles ◽  
Crystal Structure Defects

We have revealed that band gap of the material and the presence of crystal structure defects are key factors contributing to the appearance of thermal emission in dielectric nanoparticles doped with RE ions under intense laser excitation.

NUMERICAL MODELING OF RADIATION EXPOSURE ON A QUARTZ CRYSTAL STRUCTURE DEFECTS AND SIGNAL ANALYSIS THERMOLUMINESCENT

2020 ◽  
Vol 6 (4) ◽  
pp. 158-178
Author(s):  
Vladimir S. Sheinkman ◽  
Yuliya Yu. Erina ◽  
Oleg A. Simonov
Keyword(s):  
Crystal Structure ◽  
Radiation Exposure ◽  
Electron Concentration ◽  
Numerical Experiments ◽  
Quartz Crystal ◽  
Equilibrium Concentration ◽  
Band Model ◽  
Structure Defects ◽  
Crystal Structure Defects ◽  
Intense Radiation

Developing thermoluminescent (TL) dating methods for quartz-containing deposits has required a series of numerical experiments within the framework of the band model to study the rate of electron accumulation in quartz crystal structure defects under radioactive radiation. The crystal model contained two different types of electron traps and one emission center. A system of differential equations was solved numerically, relating the rates of change in the electron concentration in defects of the crystal structure and the electron concentration in the conduction band and holes in the valence band. The results have shown that the intense radiation exposure alters the dynamic equilibrium concentration of electrons in the traps, which significantly modifies the TL signal. In accordance with this, the sensitivity marker material to the radioactive dose, required for absolute dating and received by its intense radiation exposure, cannot be determined correctly. In addition, the numerical experiments have confirmed the possibility of dating the samples by the position of the TL signal’s maximum on the time axis, as well as the possibility of obtaining the dating by the TL signal’s amplitude.

Some examples of polyoxometalates crystal structure defects

2011 ◽  
Vol 67 (a1) ◽  
pp. C807-C807
Author(s):  
G. Leitus ◽  
L. J. W. Shimon ◽  
Y. Diskin-Posner ◽  
A. M. Khenkin ◽  
R. Neumann
Keyword(s):  
Crystal Structure ◽  
Structure Defects ◽  
Crystal Structure Defects

Multiscale 2D Rectangular and 3D Rhombic Gratings Created by Self-Organization of Crystal Structure Defects under Constrained Cyclic Deformation and Fracture

2007 ◽  
Vol 567-568 ◽  
pp. 421-424 ◽  
Author(s):  
Yuri Gordienko ◽  
Pavel V. Kuznetsov ◽  
Elena Zasimchuk ◽  
Rimma Gontareva ◽  
Jürgen Schreiber ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Self Organization ◽  
Ordered Structures ◽  
Structure Defects ◽  
3 Dimensional ◽  
Deformation And Fracture ◽  
Self Similar ◽  
Crystal Structure Defects ◽  
Pattern Formations ◽  
Cooperative Arrangement

The substructure evolution was observed in the range of scales from dozens nanometers to millimeters on the surface of the aluminum single crystalline plates under restricted cyclic tension. The self-similar systems of crossing bands that create the grid-like ordered structures on different scales are assumed to be clear manifestation of their self-organization. The selforganization of these grid-like structures is assumed to be inevitably related to the crystal structure defects (dislocations, point-like defects and their ensembles). The model is proposed for explanation of 2-dimensional rectangular "tweed" and 3-dimensional rhombic "pullover" pattern formations which are related to cooperative arrangement of crystal structure defects.

scholarly journals Structural Defects in TiNi-Based Alloys after Warm ECAP

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1154 ◽  
Author(s):  
Aleksandr Lotkov ◽  
Anatoly Baturin ◽  
Vladimir Kopylov ◽  
Victor Grishkov ◽  
Roman Laptev
Keyword(s):  
Crystal Structure ◽  
Positron Lifetime ◽  
Martensitic Transformations ◽  
Coarse Grained ◽  
Structural Defects ◽  
Structure Defects ◽  
Angular Pressing ◽  
Positron Lifetime Spectroscopy ◽  
Crystal Structure Defects ◽  
B2 Structure

The microstructure, martensitic transformations and crystal structure defects in the Ti50Ni47.3Fe2.7 (at%) alloy after equal-channel angular pressing (ECAP, angle 90°, route BC, 1–3 passes at T = 723 K) have been investigated. A homogeneous submicrocrystalline (SMC) structure (grains/subgrains about 300 nm) is observed after 3 ECAP passes. Crystal structure defects in the Ti49.4Ni50.6 (at%) alloy (8 ECAP passes, angle 120°, BC route, T = 723 K, grains/subgrains about 300 nm) and Ti50Ni47.3Fe2.7 (at%) alloy with SMC B2 structures after ECAP were studied by positron lifetime spectroscopy at the room temperature. The single component with the positron lifetime τ1 = 132 ps and τ1 = 140 ps were observed for positron lifetime spectra (PLS) obtained from ternary and binary, correspondingly, annealed alloys with coarse-grained structures. This τ1 values correspond to the lifetime of delocalized positrons in defect-free B2 phase. The two component PLS were found for all samples exposed by ECAP. The component with τ2 = 160 ps (annihilation of positrons trapped by dislocations) is observed for all samples after 1–8 ECAP passes. The component with τ3 = 305 ps (annihilation of positrons trapped by vacancy nanoclusters) was detected only after the first ECAP pass. The component with τ3 = 200 ps (annihilation of positrons trapped by vacancies in the Ti sublattice of B2 structure) is observed for all samples after 3–8 ECAP passes.

Gamma photoconductivity of Al2O3

1968 ◽  
Vol 46 (2) ◽  
pp. 147-156 ◽  
Author(s):  
D. J. Huntley ◽  
J. R. Andrews
Keyword(s):  
Crystal Structure ◽  
Electrical Conductivity ◽  
Cross Section ◽  
Secondary Electron ◽  
Time Curve ◽  
Structure Defects ◽  
Radiation Fields ◽  
Crystal Structure Defects ◽  
Initial Radiation ◽  
Time Required

The electrical conductivity of single-crystal and sintered Al2O3 which occurs during bombardment with y rays has been measured in radiation fields up to 106 R/h, using a 60CO source. The conductivity was different for different crystals and the largest value observed was 0.7 × 10−16 (Ω-cm-R/h)−1; the value for ruby (Al2O3 + 0.05 % Cr2O3) was 100 times smaller. The filling of traps by electrons (or holes) manifested itself during the initial radiation of a specimen as a reduced conductivity until the traps were filled: the density and cross section of these traps were ~1017 per cm3 and ~10−17 cm2, respectively. The shape of the conductivity vs. time curve during the initial radiation is explained by a model which takes into account the excitation of electrons from traps into the conduction band by the energetic electrons resulting from the gamma radiation. It is shown that this model is able to account quantitatively for the observations, if it is assumed that the time required for a secondary electron to lose energy from 10 to 2 eV is somewhat longer than the time associated with the ionization of a filled trap. Conductivity glow curves were observed in all specimens using internal polarization of the specimens and at least four distinct traps were observed with energies in the range 1–2 eV; these are thought to arise from crystal structure defects.

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