Flame Technique for High Temperature Single Crystal Weissenberg Photography (1000-3000°C)

1971 ◽  
Vol 15 ◽  
pp. 548-555
Author(s):  
M. A. Viswamitra ◽  
K. Jayalakshmi
Keyword(s):  
High Temperature ◽  
Single Crystal ◽  
Single Crystals ◽  
Water Cool ◽  
X Ray ◽  
Flame Heating ◽  
Experimental Crystal

Oxy-acetylene flame heating has been employed with an ordinary Nonius Weissenberg camera for high-temperature single-crystal studies over the the range 1000-3000°C. The regulator blow pipe is mounted horizontally on the camera track and one end of the experimental crystal (1 cm long) is heated by the vertical flame issuing out of a 0.5 mm bore nozzle* A long slot cut at the top of the film-cassette allows the flame to escape out without touching the X-ray film. The film-cassette consists of two split-halves hinged on one side so that it can be opened and slipped over the screen tubes. This arrangement avoids the necessity for removing the flame each time a new film is mounted on the camera. The goniometer arcs can be positioned during high-temperature exposures, and there is no need to water-cool the cassette up to the highest temperature. The device has been used to take photographs of MgO single crystals at 2100°C. It permits a ready application to diffractometers based on Weissenberg geometry.

Single Crystals: What They Tell About High Temperature Superconductivity

MRS Bulletin ◽  
1991 ◽  
Vol 16 (5) ◽  
pp. 31-35 ◽  
Author(s):  
Merwyn B. Brodsky
Keyword(s):  
New York ◽  
High Temperature ◽  
Single Crystal ◽  
Single Crystals ◽  
High Temperature Superconductivity ◽  
Scattering Length ◽  
X Ray Diffraction ◽  
Society Meeting ◽  
X Ray ◽  
American Physical

From the beginning of the activity in high temperature superconductivity (near the end of 1986), there were efforts to grow single crystals of the compounds. The push for single crystals arose because earlier work on Chevrelphase superconductors (e.g., PbMo6S8) or re-entrant superconductors (ErRh4B4) showed that the properties of complex superconductors were easily masked by impurities, grain boundaries, imperfectly averaged properties, etc.As early as the so-called “Woodstock of Physics” (the American Physical Society Meeting in New York, March 1987), a single-crystal, x-ray diffraction structure was given for YBa2Cu3O7-x (YBCO-123, with Tc = 93 K), the composition of which had been announced only three weeks earlier. The sample qualified as a single crystal because a single grain had been separated out for the x-ray study, although it was too small for any other measurements.But, single crystal studies are not infallible, and may not always be the best route. For instance, the aforementioned x-ray work on YBCO gave the wrong structure because the x-ray scattering length from oxygen atoms is too small to yield enough scattering intensity to locate them. It remained for neutron-scattering work with large powdered samples to give the correct orthorhombic structure, having Cu-O chains and warped Cu-O planes (see Figure 1).

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.

scholarly journals Modeling of magneto-conductivity of bismuth selenide: a topological insulator

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Yogesh Kumar ◽  
Rabia Sultana ◽  
Prince Sharma ◽  
V. P. S. Awana
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Single Crystal ◽  
Single Crystals ◽  
X Ray Diffraction ◽  
Field Range ◽  
X Ray ◽  
Bulk Carriers ◽  
Different Temperatures

AbstractWe report the magneto-conductivity analysis of Bi2Se3 single crystal at different temperatures in a magnetic field range of ± 14 T. The single crystals are grown by the self-flux method and characterized through X-ray diffraction, Scanning Electron Microscopy, and Raman Spectroscopy. The single crystals show magnetoresistance (MR%) of around 380% at a magnetic field of 14 T and a temperature of 5 K. The Hikami–Larkin–Nagaoka (HLN) equation has been used to fit the magneto-conductivity (MC) data. However, the HLN fitted curve deviates at higher magnetic fields above 1 T, suggesting that the role of surface-driven conductivity suppresses with an increasing magnetic field. This article proposes a speculative model comprising of surface-driven HLN and added quantum diffusive and bulk carriers-driven classical terms. The model successfully explains the MC of the Bi2Se3 single crystal at various temperatures (5–200 K) and applied magnetic fields (up to 14 T).

Calcium Carbodiimide Compounds Revisited – Syntheses, Single Crystal Structure Determination and Vibrational Spectra of Ca11N6[CN2]2, Ca4N2[CN2] and Ca[CN2]

2008 ◽  
Vol 63 (5) ◽  
pp. 530-536 ◽  
Author(s):  
Olaf Reckeweg ◽  
Francis J. DiSalvo
Keyword(s):  
Crystal Structure ◽  
Raman Spectrum ◽  
Single Crystal ◽  
Single Crystals ◽  
Vibrational Spectra ◽  
Structure Determination ◽  
X Ray ◽  
Characteristic Features ◽  
Reported Data ◽  
Correct Data

Single crystals of Ca11N6[CN2]2 (dark red needles, tetragonal, P42/mnm (no. 136), a = 1456.22(5), and c = 361.86(2) pm, Z = 2), Ca4N2[CN2] (transparent yellow needles, orthorhombic, Pnma (no. 62), a = 1146.51(11), b = 358.33(4), and c = 1385.77(13) pm, Z = 4) and Ca[CN2] (transparent, colorless, triangular plates, rhombohedral, R3̅m (no. 166), a = 369.00(3), and c = 1477.5(3) pm, Z = 3) were obtained by the reaction of Na2[CN2], CaCl2 and Ca3N2 (if demanded by stoichiometry) in arc-welded Ta ampoules at temperatures between 1200 - 1400 K. Their crystal structures were re-determined by means of single crystal X-ray structure analyses. Additionally, the Raman spectra were recorded on these same single crystals, whereas the IR spectra were obtained with the KBr pellet technique. The title compounds exhibit characteristic features for carbodiimide units with D∞h symmetry (d(C-N) = 121.7 - 123.8 pm and ∡ (N-C-N) = 180°). The vibrational frequencies of these units are in the expected range (Ca11N6[CN2]2: νs = 1230, νs = 2008; δ = 673/645/624 cm−1; Ca4N2[CN2]: νs = 1230, νs = 1986; δ = 672/647 cm−1; Ca[CN2]: νs = 1274, νs = 2031, δ = 668 cm−1). The structural results are more precise than the previously reported data, and with the newly attained Raman spectrum of Ca11N6[CN2]2 we correct data reported earlier.

scholarly journals Discontinuities at the melting point of bismuth

1931 ◽  
Vol 133 (821) ◽  
pp. 162-172 ◽  
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Random Distribution ◽  
Grown Crystal ◽  
Perfect Crystal ◽  
Real Property ◽  
Resistance Change ◽  
X Ray ◽  
Almost All ◽  
Brittle Crystals

During the last two or three years considerable attention has been given to the growth of single crystals of bismuth and to their physical properties. The result of this work has shown that the preparation of a good single crystal is exceedingly difficult, the process being easily disturbed in many ways, and the conclusion must be drawn that it has not yet been possible to obtain anything approaching a perfect crystal. In all cases where the grown crystal has been adequately examined, it has been necessary to admit that the supposed single crystal was full of discontinuities. This was shown by Kapitza* in his work on the growth and magneto­-resistance change of single crystals of bismuth. He found it very difficult to produce a crystal rod parallel to the hexagonal axis that was flexible. Almost all the crystals grown with this orientation were apparently brittle in that a very little strain would cause a sharp fracture parallel to the principal cleavage plane. Some crystals indeed broke up into small pieces 2 or 3 mm. long when dropped from a height of a few centimetres on a table. As the separate pieces proved to be fairly flexible this brittleness is not a real property of the crystal, but appears to be due to isolated cracks or discontinuities in the crystal (the word “crack” is used with the meaning defined by Kapitza in his paper, where further arguments for their existence from X-ray and resistance measurements are given). These cracks are not characteristic only of the brittle crystals, but appear to be present in many flexible crystals as well, their flexibility being due to a random distribution of a comparatively large number of cracks small in area compared to the dimensions of the rod.

Evaluation of Multicomponent Nickel Base LI2 and Other Intermetallic Alloys as High Temperature Structural Materials

1986 ◽  
Vol 81 ◽  
Author(s):  
D. M. Shah ◽  
D. N. Duhl
Keyword(s):  
High Temperature ◽  
Single Crystal ◽  
Single Crystals ◽  
Impact Resistance ◽  
High Strength ◽  
Structural Materials ◽  
Nickel Base Superalloy ◽  
Intermetallic Alloys ◽  
Nickel Base ◽  
Base Superalloy

AbstractMulticomponent nickel base intermetallics with the L12 structure were evaluated as high temperature structural materials. The compounds were based on the γ' composition of PWA 1480, a high strength single crystal nickel base superalloy. The best balance of properties in the compound was achieved with <111> oriented single crystals but no significant advantage could be demonstrated over the precipitation hardened superalloys. Insufficient impact resistance was a major deficiency of the L12 compounds. Other nickel base intermetallics were also evaluated but showed little advantage over superalloys.

Structural-phase transition in (Cu2Te)2−x(ZnTe)x at high temperature

2021 ◽  
pp. 2150113
Author(s):  
H. B. Gasimov ◽  
R. M. Rzayev
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
High Temperature ◽  
Single Crystals ◽  
Structural Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Range ◽  
Xrd Study ◽  
Xrd Method

Cu2Te single crystal was grown by the Bridgman method. X-ray diffraction (XRD) study of Cu2Te single crystals in the temperature range of 293–893 K was performed and possible phase transitions in the mentioned range of temperature have been investigated. (Cu2Te)[Formula: see text](ZnTe)[Formula: see text] single crystals also were grown with [Formula: see text], 0.05, 0.10 concentrations and structural properties of the obtained single crystals were investigated by the XRD method in the temperature range 293–893 K. Lattice parameters and possible phase transitions in the mention temperature range were determined for (Cu2Te)[Formula: see text](ZnTe)[Formula: see text] single crystals for [Formula: see text], 0.05, 0.10 concentrations.

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