Volatile Mixed Metal Y-Ba and Ba-Cu Precursors for Mocvd of High Tc Superconductors: A Way to Improve the Transport of Barium ?

1994 ◽  
Vol 346 ◽  
Author(s):  
Liliane G. Hubert-Pfalzgraf ◽  
Florence Labrize ◽  
Herve Guillon ◽  
Patrick Tobaly
Keyword(s):  
Mass Spectrometry ◽  
Thermal Stability ◽  
Pressure Measurements ◽  
X Ray Diffraction ◽  
High Tc Superconductors ◽  
High Tc ◽  
X Ray ◽  
Mixed Metal ◽  
Decomposition Experiments ◽  
Vapor Pressure Measurements

ABSTRACTThe fluoroisopropoxide ligand (HFIP) has allowed the synthesis of mixed-metal homoleptic Ba2Y and CuBa alkoxides. However, although these species are all volatile, their poor thermal stability precludes their use as CVD precursors. Their properties have thus been optimized by introduction of 2,2,6,6-tetramethylheptane-3,5-dione (thdH) in the metal coordination sphere. Compounds such as Y2Ba(μ-HFIP)4(thd)4, the first volatile Y-Ba species reported so far, as well as BaCu2(HFIP)4(thd)2 and YCu(HFIP)2(thd)3 have been obtained. These heterometallic ϐdiketonatoalkoxides have been characterized by a variety of techniques including X-ray diffraction, mass spectrometry, vapor pressure measurements and thermogravimetric analysis. Preliminary data on thermal decomposition experiments are given.

SYNTHESIS AND CHARACTERIZATION OF HIGH-Tc SUPERCONDUCTORS IN THE Tl–Ca–Ba–Cu–O SYSTEM

1989 ◽  
Vol 03 (05) ◽  
pp. 733-741
Author(s):  
NAROTTAM P. BANSAL ◽  
D. E. FARRELL
Keyword(s):  
Sintering Temperature ◽  
Resistive Transition ◽  
X Ray Diffraction ◽  
High Tc Superconductors ◽  
High Tc ◽  
X Ray ◽  
Resistivity Measurements ◽  
Temperature Time ◽  
Dominant Phase

In an effort to synthesize the high-T c superconducting phase in the thallium system, two nominal compositions, Tl 2 Ca 2 Ba 2 Cu 3 O 10 and Tl 1 Ca 3 Ba 1 Cu 3 O 8.5, have been investigated for superconductivity as a function of the sintering temperature, time, atmosphere, and quench rate. Samples have been characterized by electrical resistivity measurements, X-ray diffraction, and scanning electron microscopy. Samples of starting composition Tl 2 Ca 2 Ba 2 Cu 3 O 10 fired in air at 860–900°C and rapidly quenched showed T c (R = 0) of 96–107 K. In contrast, specimens of starting composition Tl 1 Ca 0 Ba 1 Cu 3 O 8.5 when baked at 900°C and slow cooled in oxygen were superconducting at ≥ 116 K and consisted of Tl 2 Ca 2 Ba 2 Cu 3 O 10+x as the dominant phase. Our results also show that, in contrast to the case of YBa 2 Cu 3 O 7−x, doping with a small concentration of fluorine sharpens the resistive transition and produces large T c increase in thallium-based superconductors.

VALENCE STATES AND LOCAL ENVIRONMENT OF THALLIUM AND COPPER IONS IN SOME NEW HIGH Tc SUPERCONDUCTORS BY XAS

1989 ◽  
Vol 03 (07) ◽  
pp. 1085-1096 ◽  
Author(s):  
F. STUDER ◽  
R. RETOUX ◽  
C. MARTIN ◽  
C. MICHEL ◽  
B. RAVEAU ◽  
...  
Keyword(s):  
Valence State ◽  
Copper Ions ◽  
Local Environment ◽  
X Ray Diffraction ◽  
High Tc Superconductors ◽  
High Tc ◽  
X Ray ◽  
Valence States ◽  
X Ray Absorption ◽  
Thallium Ions

The valence states of cations inside four high T c thallium superconductors have been investigated by X-ray absorption spectroscopy at thallium LIII , LI and copper K-edges. The thallium ions are observed on LIII and LI edges in the Tl(III) valence state (empty 6s levels) in spite of large Tl-O distances in the (a, b) plane of the structure as deduced from X-ray diffraction. The presence of two types of Tl-O distances have been well established on XANES spectra and the F.T. of EXAFS have shown the presence of two very short Tl-O bonds (2.03 Å). The copper K-edges are characterized by the absence of Cu(I) state (3d10 line).

X-ray diffraction peak-broadening analysis of (La-M)2CuO4 high-Tc superconductors

1993 ◽  
Vol 8 (1) ◽  
pp. 2-6 ◽  
Author(s):  
Davor Balzar ◽  
Hassel Ledbetter ◽  
Alexana Roshko
Keyword(s):  
Diffraction Peak ◽  
Line Profiles ◽  
X Ray Diffraction ◽  
High Tc Superconductors ◽  
Fault Probability ◽  
High Tc ◽  
X Ray ◽  
Peak Broadening ◽  
Crystallographic Symmetry ◽  
Stacking Fault Probability

An X-ray diffraction peak-broadening analysis of four oxides is described: La2CuO4 and La1.85M0.15CuO4 (M = Ca,Ba,Sr) high-Tc superconductors. The diffraction line profiles were fitted with a convolution of specimen and instrumental functions, and the specimen peakbroadening angular dependence was analyzed with the Warren-Averbach method. It was found that microstrains and incoherently diffracting domains are highly anisotropic. In the superconductors, stacking-fault probability increases with increasing Tc; microstrain decreases. In La2CuO4, different broadening of (h00) and (0k0) reflections is not caused by stacking faults; it might arise from lower crystallographic symmetry.

Novel MII (M = Mn, Fe, Co, Ni) Coordination Assemblies Based on 2-(((1-(Pyridin-n-ylmethyl)-1H-1,2,3-triazol-4-yl)methyl)thio)pyridine Ligands

2016 ◽  
Vol 69 (6) ◽  
pp. 645 ◽  
Author(s):  
Lu Jiang ◽  
Zhe Wang ◽  
Shi-Qiang Bai ◽  
Xian Jun Loh ◽  
T. S. Andy Hor
Keyword(s):  
Mass Spectrometry ◽  
Thermal Stability ◽  
Coordination Mode ◽  
X Ray Diffraction ◽  
X Ray ◽  
Pyridine Ligands ◽  
Mononuclear Complexes ◽  
Chelate Formation ◽  
Ionisation Mass Spectrometry ◽  
Ionisation Mass

Three novel 1D coordination polymers [M(L1)2(OH2)2(ClO4)2]n (M = Mn (1), Co (2)) and [Ni(L1)2(OH2)2(NO3)2]n (3), and two mononuclear complexes [Fe(L2)2(MeOH)2(ClO4)2] (4) and [Co(L2)2(OH2)2(ClO4)2] (5) were prepared from 2-(((1-(pyridin-n-ylmethyl)-1H-1,2,3-triazol-4-yl)methyl)thio)pyridine ligands (n = 4 (L1), and 2 (L2)). The complexes 1–5 were characterised by single-crystal X-ray diffraction (XRD), powder XRD, thermogravimetric analysis, elemental analysis, infrared, and electrospray ionisation mass spectrometry analyses. The complexes 1–5 showed good purity and thermal stability. The structural outcome of 1–3 is driven by the double and open-bridging coordination mode preference of the spacer L1 which favours the formation of polymeric 18-member metallomacrocycles. Use of an isomeric L2 with different picolyl nitrogen orientation, which favours chelate formation, resulted in mononuclear complexes 4 and 5. This work demonstrates a simple but powerful spacer-directed strategy to define and construct coordination frameworks tuned by different metal characters and hybrid 1,2,3-triazoles.

Thermally Stable 3,6-Disubstituted 1,2,4,5-Tetrazines

2013 ◽  
Vol 68 (12) ◽  
pp. 1310-1320 ◽  
Author(s):  
Thomas M. Klapötke ◽  
Andreas Preimesser ◽  
Jörg Stierstorfer
Keyword(s):  
Mass Spectrometry ◽  
Thermal Stability ◽  
High Thermal Stability ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
H Nmr ◽  
New Compounds ◽  
Very High ◽  
C Nmr

Several 3,6-disubstituted 1,2,4,5-tetrazines were synthesized by nucleophilic substitution using 3,6-bis-(3,5-dimethyl-pyrazol-1-yl)-1,2,4,5-tetrazine and 3,6-dichloro-1,2,4,5-tetrazine as electrophiles. All new compounds were characterized by 1H NMR, 13C NMR and vibrational spectroscopy, mass spectrometry and elemental analysis (C,H,N). For analysis of the thermostability, differential scanning calorimetry (DSC) was used. Especially, the symmetrically bis-3,5-diamino-1,2,4- triazolyl-substituted derivative shows a very high thermal stability up to 370 °C. Therefore its energetic properties were determined and compared with thoses of hexanitrostilbene (HNS). The crystal structures of 3,6-bishydrazino-1,2,4,5-tetrazine, 3,6-dichloro-1,2,4,5-tetrazine and 3-amino-6-(3,5- diamino-1,2,4-triazol-1-yl)-1,2,4,5-tetrazine dihydrate have been determined by low-temperature X-ray diffraction

Non Trivial Processes for Obtaining Bi-Based High Tc Superconductors

1998 ◽  
Vol 547 ◽  
Author(s):  
R. Cloots ◽  
M. Ausloos
Keyword(s):  
Magnetic Field ◽  
Growth Process ◽  
Main Axis ◽  
Ac Magnetic Susceptibility ◽  
X Ray Diffraction ◽  
High Tc Superconductors ◽  
High Tc ◽  
X Ray ◽  
Melt Texturing ◽  
Scanning Electron

AbstractDysprosium doped Bi-based 2212 ceramics were synthesized by a melt-texturing growth process in a 1.2T magnetic field, applied perpendicularly to the main axis of a cylindrically shaped sample. The materials were characterized by X-ray diffraction, optical and scanning electron microscopy and energy dispersive X-ray analyses. The texturing process was optimized with respect to the sample electrical resistivity and AC magnetic susceptibility.

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