Thermal hysteresis of the dielectric constant and anomalous behaviour of the raman soft mode damping of Cd2Nb2O7

Smolensky, G. A.; Колпакова, Н. Н.; Kizhaev, S. A.; Sher, Eran

doi:10.1080/00150198708227915

Cited by 13 publications

(1 citation statement)

References 23 publications

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“…Both the dielectric constant and the heat capacity indicate that the former transition is of second order, while a first-order character is found for the latter transition [10]. Based on the results from Raman scattering [19,20], dielectric constant [19], and heat capacity measurements [10], an incommensurate structure has been suggested for the phase between T 3 and T 4 . However, previous x-ray diffraction measurements [16,21] only reported an average symmetry of monoclinic Cc below T 3 , with no evidence of incommensurate satellite peaks.…”

Section: Introductionmentioning

confidence: 98%

X-ray scattering studies of structural phase transitions in pyrochlore Cd₂Nb₂O₇

Tachibana

Fritsch

Gaulin

2013

J. Phys.: Condens. Matter

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Structural phase transitions in pyrochlore Cd2Nb2O7 were studied by means of single crystal x-ray scattering. On cooling below the ferroelastic transition at T1 = 204 K, the cubic Bragg peaks broaden in a manner consistent with weak orthorhombic distortion. The distortion evolves rather smoothly through the ferroelectric transition at T2 = 196 K, which explains the absence of sharp anomalies in the heat capacity and dielectric constant at this transition. At lower temperatures, the anomalous relaxor-like character of this compound is evident as a gradual reduction in the Bragg peak intensities, which continues down to the onset of another transition at T3 = 85 K. The studies of two Bragg peaks that are forbidden within the cubic phase reveal an interesting disparity: while the intensity for one of them increases in a classical mean-field manner below T1, the other shows unconventional behavior that is reminiscent of the pyrochlore superconductor Cd2Re2O7.

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Section: Introductionmentioning

confidence: 98%

X-ray scattering studies of structural phase transitions in pyrochlore Cd₂Nb₂O₇

Tachibana

Fritsch

Gaulin

2013

J. Phys.: Condens. Matter

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Phase diagram of ice in the VII–VIII–X domain. Vibrational and structural data for strongly compressed ice VIII

Pruzan

Chervin

Wolanin

et al. 2003

J Raman Spectroscopy

120

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The first part of this paper presents a short survey on the phase diagram of ice in the pressure range from 2 to 100 GPa from 10 to 300 K. The description is mainly devoted to the problem of the symmetrization of the O -H· · ·O bond, that is, the transformation of ice VII or VIII to ice X. In connection with this introduction, in the second part of the paper new vibrational and structural data obtained from Raman scattering and x-ray diffraction in ice VIII are given and these properties are compared with those of ice VII. Specifically, below 100 K, solid VIII vanishes at 62 GPa to give birth to a state which is the first step to ice X. This transition is marked by a softening of the lowest Raman-active lattice mode and the disappearance of the Raman signal. During the compression of ice VIII the O-H stretching mode wavenumber shows soft mode behaviour. It is found that the expansivity of ice VIII is negative above 10 GPa.

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