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Acoustic attenuation in ferroelectric Sn2P2S6 crystals

100%

Kohutych A. , Yevych R. , Perechinskii S. , Vysochanskii Y.

Open Physics

2010

tom 8

nr 6

905-914

The temperature and frequency dependencies of sound attenuation for the proper uniaxial ferroelectric Sn2P2S6, which has a strong nonlinear interaction of the polar soft optic and fully symmetrical optic modes that is related to the triple well potential, were studied by Brillouin spectroscopy. It was found that the sound velocity anomaly is described in the Landau-Khalatnikov approximation with one relaxation time. For explanation of the observed temperature and frequency dependencies of the sound attenuation in the ferroelectrric phase, the accounting of several relaxation times is needed and, for quantitative calculations, the mode Gruneisen coefficients are more appropriate as interacting parameters than are the electrostrictive coefficients. Relaxational sound attenuation by domain walls also appears in the ferroelectric phase of Sn2P2S6 crystals.

Molecular impurity ions as centres with charge transfer degrees of freedom. Influence on ferroelectric phase transitions.

100%

Vikhnin V. S. , Maksimowa T. I. , Hanuza J.

Materials Science Poland

2005

tom Vol. 23, No. 3

677--684

The concept of molecular impurity ions (MI) as centres with charge transfer degrees of freedom, interacting (through the order parameter of the phase transition) with local vibrations and non-soft phonons, as well as with light, has been developed. It has been shown that MI can significantly influence a ferroelectric phase transition (FPT) due to a direct interaction of their specific charge transfer degrees of freedom with the ferroelectric order parameter. In this work, we predict a significant increase of the FPT critical temperature when increasing the MI concentration. The e MnO4- molecular impurity ions embedded in ferroelectric crystals (e.g. molybdates, tungstates, chromates, phosphates) are considered as possible candidates capable of inducing this effect.

Elastic properties of (PbySn1−y )2P2S6 solid solutions

88%

Bilanych R. , Yevych R. , Kohutych A. , Perechinskii S. , Stoika I. , Vysochanskii Y.

Open Physics

2014

tom 12

nr 9

611-614

Elastic properties of (PbySn1−y )2P2S6 solid solutions were studied using Brillouin scattering technique. Different scattering geometries were used for sound velocities determination that make it possible to find all components of the stiffness tensor. The concentration dependencies of volume compressibility, the Grüneisen parameter and Debye temperature were investigated. The results obtained were used to analyze chemical bonding with substitution of tin by lead at room temperature in the crystals under consideration.