Substitutions in Hg-cuprate superconductors

1994 ◽  
Vol 9 (11) ◽  
pp. 2809-2813 ◽  
Author(s):  
V. Kirtikar ◽  
K.K. Singh ◽  
D.E. Morris
Keyword(s):  
High Pressure ◽  
Low Temperature ◽  
Magnetization Curve ◽  
Cuprate Superconductors ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lattice Constants ◽  
Superconducting Compounds ◽  
Low Temperature Phase

Several substitutions have been attempted in the Hg layer of the Hg 1212 and 1223 cuprate superconductors. A new series of (Hg,Bi)1212 superconducting compounds has been synthesized. The highest Tc of the series (92 K) is found for the composition (Hg0.67Bi0.33)Sr2(Y0.5Ca0.5)Cu2O7−δ, with lattice constants a = 3.811 Å and c = 12.002 Å. X-ray diffraction and SEM with EDX analysis confirm that Hg is indeed incorporated in the structure. High-pressure oxygenation at 250 bar and 400 °C changes the magnetization curve, adding a second transition at ∼42 K; the 92 K transition remains unchanged. High-pressure oxygenation of Pb-substituted composition of the 1223 system, (Hg0.67Pb0.33)Ba2Ca2Cu3O8 also leads to the formation of low temperature phase with Tc = 67 K. The low Tc phase is associated with the incorporation of extra oxygen, possibly in the Hg layer.

A low temperature phase of (NH4)2TeBr6

1969 ◽  
Vol 47 (22) ◽  
pp. 4288-4289 ◽  
Author(s):  
A. K. Das ◽  
I. D. Brown
Keyword(s):  
Low Temperature ◽  
Tetragonal Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Low Temperature Phase

X-Ray diffraction has shown the existence of a low temperature tetragonal phase of (NH4)2TeBr6 having space group P4/mnc(D4h6) with a = 7.501, c = 10.765 Å.

X-ray diffraction study of the phase transition of K2Mn2(BeF4)3: a new type of low-temperature structure for langbeinites

2001 ◽  
Vol 57 (3) ◽  
pp. 221-230 ◽  
Author(s):  
A. Guelylah ◽  
G. Madariaga ◽  
V. Petricek ◽  
T. Breczewski ◽  
M. I. Aroyo ◽  
...  
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Mode Analysis ◽  
Cubic Phase ◽  
Temperature Phase ◽  
Temperature Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
New Type ◽  
Low Temperature Phase

The potassium manganese tetrafluoroberyllate langbeinite compound has been studied in the temperature range 100–300 K. Using DSC measurements, a phase transition has been detected at 213 K. The space group of the low-temperature phase was determined to be P1121 using X-ray diffraction experiments and optical observations of the domain structure. The b axis is doubled with respect to the prototypic P213 cubic phase. Lattice parameters were determined by powder diffraction data [a = 10.0690 (8), b = 20.136 (2), c = 10.0329 (4) Å, γ = 90.01 (1)°]. A precise analysis of the BeF4 tetrahedra in the low-temperature phase shows that two independent tetrahedra rotate in opposite directions along the doubled crystallographic axis. A symmetry mode analysis of the monoclinic distortion is also reported. This is the first report of the existence of such a phase transition in K2Mn2(BeF4)3 and also of a new type of low-temperature structure for langbeinite compounds.

X-Ray Diffraction Study of the Low Temperature Phase of Rubidium Cyanide

1996 ◽  
Vol 65 (7) ◽  
pp. 2099-2105 ◽  
Author(s):  
Yukio Yoshimura ◽  
Seiichi Shinohara ◽  
Noritoshi Tsuda ◽  
Hiroshi Iwasaki
Keyword(s):  
Low Temperature ◽  
Diffraction Study ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Low Temperature Phase

X-Ray Diffractometric Examination of Low-Temperature Phase Transformations in Single-Crystal Strontium Titanate

1963 ◽  
Vol 7 ◽  
pp. 136-145 ◽  
Author(s):  
Farrel W. Lytle
Keyword(s):  
Low Temperature ◽  
Single Crystal ◽  
Lattice Parameter ◽  
Temperature Curve ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Tetragonal Modification ◽  
X Ray ◽  
Line Splitting ◽  
Low Temperature Phase

AbstractThe lattice parameters of single-crystal SrTiO2 were determined by X-ray diffraction as a function of temperature from 4.2 to 300°K. Three significant regions were found: from 65 to 110°K a tetragonal modification, exists (c/a = 1.00056); from 35 to 55°K, line splitting consistent with orthorhornbic symmetry was observed, and at 10°K an anomalous maximum in the lattice parameter vs. temperature curve was found which suggested a third structure transformation. In the tetragonal region (at 78°K) the formation of a domain structure was observed with a polarising microscope. The low-temperature X-ray technique and X-ray cryostat are described.

X-Ray Diffraction Study of the Low Temperature Phase Transitions of CuBrTe and CuITe

1992 ◽  
Vol 61 (12) ◽  
pp. 4659-4660 ◽  
Author(s):  
Takashi Sakuma ◽  
Tadahiro Kaneko ◽  
Haruyuki Takahashi ◽  
Kōji Honma ◽  
Robert B. Beeken
Keyword(s):  
Phase Transitions ◽  
Low Temperature ◽  
Diffraction Study ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Low Temperature Phase
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