Study of molten zone profile and defect formation during laser heated pedestal growth

2019 ◽  
Author(s):  
Bo Liu ◽  
Yang Yu ◽  
Subhabrata Bera ◽  
Michael P. Buric ◽  
Benjamin Chorpening ◽  
...  
Keyword(s):  
Defect Formation ◽  
Molten Zone ◽  
Laser Heated

Growth of Single Crystal Yig Fibers by the Laser Heated Pedestal Growth Method

1997 ◽  
Vol 481 ◽  
Author(s):  
HanJin Lim ◽  
R. C. DeMattei ◽  
R. S. Feigelson
Keyword(s):  
Single Crystal ◽  
Growth Rates ◽  
Decomposition Temperature ◽  
Molten Zone ◽  
Nominal Composition ◽  
Vis Spectroscopy ◽  
Growth Method ◽  
Crystal Fibers ◽  
Iron Garnet ◽  
Laser Heated

ABSTRACTYttrium iron garnet (YIG) single crystal fibers of nominal composition Y3Fe5O12 were grown by the laser heated pedestal growth (LHPG) technique, a miniaturized floated-zone process. YIG which melts incongruently, was grown at a temperature below the peritectic decomposition temperature under self-adjusting conditions even though it has very narrow solidification region according to the Y2O3-Fe2O3 phase diagram. YIG fibers in diameter ranges from 100 to 750 μm were grown at various growth rates and conditions, and analyzed by x-ray diffraction, electron microprobe, and IR-VIS spectroscopy. Infrared transparent YIG fibers were grown at rates below 12 mm/h in air. At these growth rates, yttrium orthoferrite and iron-oxide inclusions within the YIG fiber, which act as IR scattering centers, were significantly reduced. The transparency of the fibers was more dependent on the growth rate than the stability of the molten zone. Surface ridges containing an Fe-rich composition were observed at all growth rates. These were associated with molten zone instability.

Structure of superconducting fibers prepared by laser-heated pedestal growth method

1990 ◽  
Vol 48 (4) ◽  
pp. 30-31
Author(s):  
L.Y. Cai ◽  
Y.J. Huo ◽  
S.N. Mao ◽  
M.L. Liu ◽  
F.H. Li
Keyword(s):  
Critical Current Density ◽  
Laser Beam ◽  
Critical Current ◽  
Transition Region ◽  
Current Density ◽  
Raw Material ◽  
Molten Zone ◽  
Growth Method ◽  
Laser Heated ◽  
Critical Current Density Jc

Superconducting fibers have drawn great attention because of the latent prospect for applications. Fibers of superior quality were obtained by means of the laser-heated pedestal growth (LHPG) method. For LHPG method a fine laser beam is focused at the “source rod” made of raw material so that a small molten zone is formed on its upper end. Then a seed crystal is introduced into the melt and drawn from it to grow crystalline fibers. In this paper the structure of bismuth based Bi-Sr-Ca-Cu-O and Bi-Pb-Sr-Ca-Cu-O superconducting fibers prepared by LHPG is reported. The values of Tc for the two kinds of fibers are 85k and 108k respectively. The critical current density Jc can reach 5150A/cm2. The diameters of fibers are ranged from 35μm-200μm. The thin fibers are flexible.Fig.1 shows the transition region between the source rod (R) and the LHPG fiber (G). It indicates that the source crystal first melts and then recrystallizes along a certain cry stenographic direction.

Experiment and simulation on interface shapes of an yttrium aluminium garnet miniature molten zone formed using the laser-heated pedestal growth method for single-crystal fibers

2009 ◽  
Vol 42 (4) ◽  
pp. 553-563 ◽  
Author(s):  
P. Y. Chen ◽  
C. L. Chang ◽  
K. Y. Huang ◽  
C. W. Lan ◽  
W. H. Cheng ◽  
...  
Keyword(s):  
Control Volume ◽  
Molten Zone ◽  
Yttrium Aluminium Garnet ◽  
Zone Length ◽  
Yttrium Aluminium ◽  
Growth Method ◽  
Dimensional Simulation ◽  
Stable Growth ◽  
Crystal Fibers ◽  
Laser Heated

A two-dimensional simulation was employed to study the melt/air and melt/solid interface shapes of the miniature molten zone formed in a laser-heated pedestal growth (LHPG) system. Using a non-orthogonal body-fitting grid system with the control-volume finite-difference method, the interface shape can be determined both efficiently and accurately. During stable growth, the dependence of the molten-zone length and shape on the heating CO2laser is examined in detail under both the maximum and the minimum allowed powers with various growth speeds. The effect of gravity on the miniature molten zone is also simulated and the possibility of horizontally oriented LHPG is revealed. Such a horizontal system is good for the growth of long crystal fibers.

Xenon ion irradiation of superconducting YBa2Cu3O7 thin films

1990 ◽  
Vol 48 (4) ◽  
pp. 92-93
Author(s):  
H. Watanabe ◽  
B. Kabius ◽  
B. Roas ◽  
K. Urban
Keyword(s):  
Defect Formation ◽  
Ion Irradiation ◽  
High Resolution Electron Microscopy ◽  
Structural Disorder ◽  
Flux Lines ◽  
Pinning Effect ◽  
Magnetic Flux Lines ◽  
Resolution Electron ◽  
Radiation Induced ◽  
Induced Defects

Recently it was reported that the critical current density(Jc) of YBa2Cu2O7, in the presence of magnetic field, is enhanced by ion irradiation. The enhancement is thought to be due to the pinning of the magnetic flux lines by radiation-induced defects or by structural disorder. The aim of the present study was to understand the fundamental mechanisms of the defect formation in association with the pinning effect in YBa2Cu3O7 by means of high-resolution electron microscopy(HRTEM).The YBa2Cu3O7 specimens were prepared by laser ablation in an insitu process. During deposition, a substrate temperature and oxygen atmosphere were kept at about 1073 K and 0.4 mbar, respectively. In this way high quality epitaxially films can be obtained with the caxis parallel to the <100 > SrTiO3 substrate normal. The specimens were irradiated at a temperature of 77 K with 173 MeV Xe ions up to a dose of 3.0 × 1016 m−2.

Defect formation in solids by decay of electronic excitations

1985 ◽  
Vol 147 (11) ◽  
pp. 523 ◽  
Author(s):  
M.I. Klinger ◽  
Ch.B. Lushchik ◽  
T.V. Mashovets ◽  
G.A. Kholodar' ◽  
M.K. Sheinkman ◽  
...  
Keyword(s):  
Defect Formation ◽  
Electronic Excitations

INFLUENCE OF THE LOCATION OF THE BASEBOARD JUMPER FOR FIRMWARE FOR DEFECT FORMATION IN CHAIN DRIVE SPROCKET FORGING

2020 ◽  
Author(s):  
I.A. Tserna ◽  
◽  
V.V. Bukhov ◽  
Keyword(s):  
Computer Simulation ◽  
Defect Formation ◽  
Chain Drive ◽  
Combine Harvester

The paper presents the results of computer simulation of the process of de-formationforged chain wheels, combine harvester; the influence of the placement of the jumper outline for firmware on the processes of defect formation in forging.

Solutocapillary-convection-driven macrovoid defect formation in polymeric membranes

2001 ◽  
Author(s):  
J. Zartman ◽  
V. Khare ◽  
A. Greenberg ◽  
M. Pekny ◽  
P. Todd ◽  
...  
Keyword(s):  
Defect Formation ◽  
Polymeric Membranes

Reasons for the formation of crack-like defects in 09Г2С heavy plate steel for tank steel structures

2020 ◽  
Vol 10 (5) ◽  
pp. 479-489
Author(s):  
Vitaly М. Goritsky ◽  
◽  
Georgy R. Shneyderov ◽  
Eugeny P. Studenov ◽  
Olga A. Zadubrovskaya ◽  
...  
Keyword(s):  
Impact Toughness ◽  
Defect Formation ◽  
Steel Structures ◽  
Controlled Rolling ◽  
Plate Steel ◽  
Heavy Plate ◽  
Oil Storage ◽  
Magnetic Inspection ◽  
Metal Microstructure

Determination of causes of crack-like defects in the heavy plate steel 09Г2С is a crucial task, the solution of which is aimed at improving the mechanical safety of oil storage steel vertical tanks. In order to determine the causes for the formation of a group of crack-like defects oriented towards rolling, revealed during grinding and magnetic inspection of the tank wall surface near the vertical weld, the analysis of the chemical composition and testing of the mechanical properties of heavy plate steel were carried out, including the determination of the anisotropy of impact toughness in the temperature range from +20 to –75 °С, analysis of metal microstructure in the area of defect formation on transversal sections and rolled surface. Impact bending tests of 09Г2С heavy plate steel after controlled rolling in longitudinal and transverse directions showed no anisotropy of impact toughness, as well as high purity of steel as for sulfur and titanium, which at higher content causes impact toughness anisotropy. The revealed features of metal microstructure near the defects made it possible to conclude that the crack-like defects were formed during the rolling of gas bubbles at the stage of preparing semi-finished rolled products for finishing rolling. One of the possible methods to prevent such defects from getting into finished rolled products is the use of automated systems of visual inspection of rolled products in the manufacturing process.

Micro-Raman Spectroscopy Evaluation of the Local Mechanical Stress in Shallow Trench Isolation CMOS Structures: Correlation with Defect Generation and Diode Leakage

1998 ◽  
Author(s):  
I. De Wolf ◽  
G. Groeseneken ◽  
H.E. Maes ◽  
M. Bolt ◽  
K. Barla ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Mechanical Stress ◽  
Defect Formation ◽  
Active Area ◽  
Wet Oxidation ◽  
Leakage Currents ◽  
Shallow Trench Isolation ◽  
Micro Raman Spectroscopy ◽  
Silicon Devices ◽  
Trench Isolation

Abstract It is shown, using micro-Raman spectroscopy, that Shallow Trench Isolation introduces high stresses in the active area of silicon devices when wet oxidation steps are used. These stresses result in defect formation in the active area, leading to high diode leakage currents. The stress levels are highest near the outer edges of line structures and at square structures. They also increase with decreasing active area dimensions.

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