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

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.

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The low-temperature phase sequence gamma - delta - epsilon in halide perovskite tetramethylammonium trichlorogermanate(II) studied by X-ray diffraction

Journal of Physics Condensed Matter ◽

10.1088/0953-8984/7/26/005 ◽

1995 ◽

Vol 7 (26) ◽

pp. 4983-4998 ◽

Cited By ~ 5

Author(s):

K Futterer ◽

R L Withers ◽

T R Welberry ◽

W Depmeier

Keyword(s):

Low Temperature ◽

Temperature Phase ◽

X Ray Diffraction ◽

Gamma Delta ◽

X Ray ◽

Phase Sequence ◽

Halide Perovskite ◽

Low Temperature Phase

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

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768100019960 ◽

2001 ◽

Vol 57 (3) ◽

pp. 221-230 ◽

Cited By ~ 1

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.

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Substitutions in Hg-cuprate superconductors

Journal of Materials Research ◽

10.1557/jmr.1994.2809 ◽

1994 ◽

Vol 9 (11) ◽

pp. 2809-2813 ◽

Cited By ~ 1

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.

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