Critical Current of Bi-2212 Single Crystal by Doping Oxides as a Pinning Center

2014 ◽  
Vol 95 ◽  
pp. 175-180
Author(s):  
Takuya Agou ◽  
Hiroya Imao
Keyword(s):  
Rare Earth ◽  
Single Crystal ◽  
Single Crystals ◽  
Crystal Surface ◽  
Rare Earth Oxides ◽  
Pinning Centers ◽  
Current Path ◽  
Pinning Center ◽  
Superconducting Current ◽  
A Current

It is necessary to formpinning centers in superconductors to allow the flow of large currents throughthe specimens. To clarify the properties of pinning centers, it is preferableto investigate single crystals. In this study, heat treatment was used to dopevarious oxides into Bi2Sr2CaCu2Ox(Bi-2212) single crystals prepared by self-flux methods and the criticalcurrent (Ic) was measured. The oxides used in this study were Al2O3and the rare earth oxides Er2O3and Nd2O3. At 77K, Nd2O3and Er2O3 are magnetic, whereas Al2O3is nonmagnetic. The Ic of the samples were measured as a current per width of 1cm (Ics). The resulting Ics of the Bi-2212 single crystal was 2.8A/cm and thatof the Al2O3 doped Bi-2212 sample was 4.5A/cm. Comparedwith these samples, doping the other rare earth oxides gave Ics values inexcess 10A/cm. The results indicated that the doping oxides were effective inoperating as pinning centers in the samples. We assumed the current path in asingle crystal, and calculated the Ics by superconducting current simulation.The results indicated that the oxides permeated from a crystal surface in aporous shape. The oxides increase the current which flow in the Cu-O2planes that are parallel to the a-b plane.

scholarly journals Potential of using inert gas flows for controlling the quality of as-grown silicon single crystal

2020 ◽  
Vol 6 (1) ◽  
pp. 1-7
Author(s):  
Tatyana V. Kritskaya ◽  
Vladimir N. Zhuravlev ◽  
Vladimir S. Berdnikov
Keyword(s):  
Single Crystal ◽  
Carbon Content ◽  
Single Crystals ◽  
Gas Flow ◽  
Thermal Stresses ◽  
Crystal Surface ◽  
Gas Flows ◽  
Reaction Products ◽  
Crystal Silicon ◽  
Argon Gas

We have improved the well-known Czochralski single crystal silicon growth method by using two argon gas flows. One flow is the main one (15–20 nl/min) and is directed from top to bottom along the growing single crystal. This flow entrains reaction products of melt and quartz crucible (mainly SiO), removes them from the growth chamber through a port in the bottom of the chamber and provides for the growth of dislocation-free single crystals from large weight charge. Similar processes are well known and have been generally used since the 1970s world over. The second additional gas flow (1.5–2 nl/min) is directed at a 45 arc deg angle to the melt surface in the form of jets emitted from circularly arranged nozzles. This second gas flow initiates the formation of a turbulent melt flow region which separates the crystallization front from oxygen-rich convective flows and accelerates carbon evaporation from the melt. It has been confirmed that oxygen evaporated from the melt (in the form of SiO) acts as transport agent for nonvolatile carbon. Commercial process implementation has shown that carbon content in as-grown single crystals can be reduced to below the carbon content in the charge. Single crystals grown with two argon gas flows have also proven to have highly macro- and micro-homogeneous oxygen distributions, with much greater lengths of single crystal portions in which the oxygen concentration is constant and below the preset limit. Carbon contents of 5–10 times lower than carbon content in the charge can be achieved with low argon gas consumption per one growth process (15–20 nl/min vs 50–80 nl/min for conventional processes). The use of an additional argon gas flow with a 10 times lower flowrate than that of the main flow does not distort the pattern of main (axial) flow circumvention around single crystal surface, does not hamper the “dislocation-free growth” of crystals and does not increase the density of microdefects. This suggests that the new method does not change temperature gradients and does not produce thermal shocks that may generate thermal stresses in single crystals.

Crystal chemistry of hydrothermally grown ternary alkali rare earth fluorides

2015 ◽  
Vol 71 (6) ◽  
pp. 768-776 ◽  
Author(s):  
Colin D. McMillen ◽  
Sara Comer ◽  
Kyle Fulle ◽  
Liurukara D. Sanjeewa ◽  
Joseph W. Kolis
Keyword(s):  
Rare Earth ◽  
Single Crystal ◽  
Single Crystals ◽  
Structural Information ◽  
Structure Type ◽  
Crystal Structure Analysis ◽  
Structural Variations ◽  
Ionic Radii ◽  
Wide Range ◽  
Potential Applications

The structural variations of several alkali metal rare earth fluoride single crystals are summarized. Two different stoichiometric formulations are considered, namely those of ARE2F7 and ARE3F10 (A = K, Rb, Cs; RE = Y, La–Lu), over a wide range of ionic radii of both the alkali and rare earth (RE) ions. Previously reported and several new single-crystal structures are considered. The new single crystals are grown using hydrothermal methods and the structures are compared with literature reports of structures grown from both melts and hydrothermal fluids. The data reported here are combined with the literature data to gain a greater understanding of structural subtleties surrounding these systems. The work underscores the importance of the size of the cations to the observed structure type and also introduces synthetic technique as a contributor to the same. New insights based on single-crystal structure analysis in the work introduce a new disordered structure type in the case of ARE2F7, and examine the trends and boundaries of the ARE3F10 stoichiometry. Such fundamental structural information is useful in understanding the potential applications of these compounds as optical materials.

A novel approach to prepare polymer mixed-brushes via single crystal surface patterning

RSC Advances ◽  
2014 ◽  
Vol 4 (33) ◽  
pp. 17071-17082 ◽  
Author(s):  
S. Abbaspoor ◽  
F. Abbasi ◽  
S. Agbolaghi
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Crystal Surface ◽  
Surface Patterning ◽  
Single Crystal Surface ◽  
Novel Approach ◽  
Surface Morphologies

Single crystals having matrix-dispersed surface morphologies were prepared and characterized.

Ein Beitrag zur Kristallchemie dreiwertiger Seltenerdoxide Zur Stabilisierung der monoklinen B-Form / About the Crystal Chemistry of Three-Valent Rare Earth Oxides The Stabilisation of the Monoclinic B-Modification

1977 ◽  
Vol 32 (5) ◽  
pp. 495-498 ◽  
Author(s):  
W. Muschick ◽  
Hk. Müller-Buschbaum
Keyword(s):  
Crystal Structure ◽  
Rare Earth ◽  
High Temperature ◽  
Single Crystals ◽  
Rare Earth Oxides ◽  
Temperature Reaction ◽  
Crystal Data ◽  
X Ray ◽  
High Temperature Reaction ◽  
Type Crystal

Single crystals of 1—x Ho2O3 : xCaO (x = 0.07), CaHoO2.5 (A) and Ca0.5Ho1.5O2.75 (B) were prepared by high temperature reaction and investigated with X-ray single crystal data. It can be shown that small amounts of CaO stabilize the monoclinic B-Typ of rare earth oxides. Phase (A) and (B) cannot be seen as a stabilized B-type crystal because they have an new crystal structure with space groupC22h–P 21/m, a = 656.6, b = 356.7, c = 529.4 pm, β = 92.3°; a = 650.2, b = 352.4, c = 584.5, β = 92.3°.

Particles and Single Crystals of Rare Earth Oxides

ChemInform ◽  
2006 ◽  
Vol 37 (1) ◽  
Author(s):  
N. Imanaka ◽  
T. Masui
Keyword(s):  
Rare Earth ◽  
Single Crystals ◽  
Rare Earth Oxides

scholarly journals Opportunity to use inert gas flow for control of qualitative characteristics of the grown silicon single crystals

2020 ◽  
Vol 22 (3) ◽  
pp. 158-167
Author(s):  
T. V. Kritskaya ◽  
V. N. Zhuravlev ◽  
V. S. Berdnikov
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Gas Flow ◽  
Thermal Stresses ◽  
Crystal Surface ◽  
Czochralski Method ◽  
Main Flow ◽  
Reaction Products ◽  
Volatile Carbon ◽  
Qualitative Characteristics

The process of growing silicon single crystals by the Czochralski method has been improved, which involves the use of two argon streams. 1st, the main flow, 15—20 nl/min, is directed from top to bottom along the growing single crystal. It captures the reaction products of the melt with a quartz crucible (mainly SiO), removes them from the chamber through a nozzle in the lower part of the chamber and provide dislocation-free single crystals from large loads. Similar processes are known and widely used in world practice since the 1970s. 2nd, additional flow, 1.5—2 nl/min, is directed at an angle of 45° to the surface of the melt in the form of jets from nozzles arranged in a ring. This flow initiates the formation of a region of turbulent melt flow, which isolates the crystallization front from convective flows enriched with oxygen, and also enhances the evaporation of carbon from the melt. It is confirmed that the oxygen evaporated from the melt (in the form of SiO) is a «transport» for non-volatile carbon. Carrying out industrial processes showed that the carbon content in the grown single crystals can be significantly reduced, up to values smaller than in the feedstock. In single crystals grown using two argon streams, an increased macro- and micro-uniformity of the oxygen distribution, a significantly larger crystal length with a given, constant oxygen concentration, were also recorded. Achieving a carbon concentration of 5 to 10 times less than in the feedstock is possible with small amounts of argon for melting (15—20 nl/min compared to 50—80 nl/min used in conventional processes. The use of an additional argon flow, which has an outflow intensity 10 times lower than that of the main flow, does not distort the nature of the flow around the single crystal surface (“axial”), does not disrupt the growth of a dislocation-free single crystal, does not increase the density of microdefects, which indicates the absence of changes in temperature gradients and thermal shock leading to thermal stresses in a single crystal.

The quaternary arsenide oxides Ce9Au5–xAs8O6 and Pr9Au5–xAs8O6

2016 ◽  
Vol 71 (12) ◽  
pp. 1245-1252
Author(s):  
Timo Bartsch ◽  
Rolf-Dieter Hoffmann ◽  
Rainer Pöttgen
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Single Crystal ◽  
Crystal Chemistry ◽  
Structure Type ◽  
Rare Earth Oxides ◽  
Gold Powder ◽  
X Ray ◽  
Annealing Temperatures ◽  
Oxide Crystal

AbstractThe quaternary gold arsenide oxides Ce9Au5−xAs8O6 and Pr9Au5−xAs8O6 were synthesized from the rare earth elements (RE), rare earth oxides, arsenic and gold powder at maximum annealing temperatures of 1173 K. The structures were refined from single crystal X-ray diffractometer data: Pnnm, a=1321.64(6) pm, b=4073.0(3), c=423.96(2), wR2=0.0842, 3106 F2 values, 160 variables for Ce9Au4.91(4)As8O6 and Pnnm, a=1315.01(4), b=4052.87(8), c=420.68(1) pm, wR2=0.0865, 5313 F2 values, 160 variables for Pr9Au4.75(1)As8O6. They represent a new structure type and show a further extension of pnictide oxide crystal chemistry. A complex polyanionic gold arsenide network [Au5As8]15− (with some disorder in the gold substructure) is charge compensated with polycationic strands of condensed edge-sharing O@RE4/4 and O@RE4/3 tetrahedra ([RE4O3]212+) as well as RE3+ cations in cavities.

Rhodium-rich silicides RERh6Si4 (RE=La, Nd, Tb, Dy, Er, Yb)

2017 ◽  
Vol 72 (11) ◽  
pp. 775-780
Author(s):  
Daniel Voßwinkel ◽  
Rainer Pöttgen
Keyword(s):  
Rare Earth ◽  
Single Crystal ◽  
Single Crystals ◽  
Three Dimensional ◽  
X Ray ◽  
Arc Melting ◽  
Covalently Bonded ◽  
Reactive Flux ◽  
The Rare Earth

AbstractPolycrystalline RERh6Si4 (RE=La, Nd, Tb, Dy, Er, Yb) samples can be synthesized by arc-melting of the elements. Single crystals of LaRh6Si4, NdRh6Si4 and YbRh6Si4 were synthesized from the elements in bismuth fluxes (non-reactive flux medium). The structures were refined on the basis of single-crystal X-ray diffractometer data: LiCo6P4 type, P6̅m2, a=700.56(3), c=380.55(1) pm, wR2=0.0257, 317 F2 values, 19 variables for LaRh6Si4, a=698.4(5), c=377.7(2) pm, wR2=0.0578, 219 F2 values, 19 variables for NdRh6Si4 and a=696.00(3), c=371.97(1) pm, wR2=0.0440, 309 F2 values, 19 variables for YbRh6Si4. The rhodium and silicon atoms build up three-dimensional, covalently bonded [Rh6Si4]δ− polyanionic networks with Rh–Si distances ranging from 239 to 249 pm. The rare earth atoms fill larger cavities within channels of these networks and they are coordinated by six silicon and twelve rhodium atoms in the form of hexa-capped hexagonal prisms.

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