Home
page
Other articles
in this issue
|
Thermal Expansion
and Phase Transformation Observation in Cs2BX4 (B=Hg, Cd; X=Br, Cl) Crystals
1. Cs2HgCl4 crystals
Krupych O., Girnyk I., Trach
I., Vlokh R., Vlokh O.
Institute of Physical Optics, 23 Dragomanov Str., 79005,
Lviv, Ukraine
download full version
The results of thermal expansion
study and the domain structure observation in Cs2HgCl4 crystals are presented.
It is shown that the phase transformations in caesium mercury chloride
crystals pass through the heterophase regions. The phase transition between
the normal and incommensurate (IC) phases is of the first order. The observed
“devil’s staircase” in the range 143K<T<181K means that the wave
vector of the modulated structure has a jump-like temperature dependence,
leading to appearance of a complicated sequence of commensurate and IC
phases. The non-compatible, inhomogeneous deformations existing in the
temperature range 183K<T<225K are, most probably, the reason for
appearing the electric polarization. The appearance of ferroelastic domains
at 8K below Tc1 is explained by the existing heterophase structure.
Key words: incommensurate phase,
domain structure, thermal expansion.
PACS: 65.70.+y, 77.80.Dj, 78.20.Fm
doi 10.3116/16091833/4/4/155/2003 |
|
1. Cummins H, 1990. Phys. Rep. 185: 211.
doi:10.1016/0370-1573(90)90058-A
http://dx.doi.org/10.1016/0370-1573(90)90058-A
2. Vlokh OG, Kityk AV, 2002. Crystalline dielectrics with incommensurately
modulated structure. Lviv.
3. Altermatt D, Arend H, Gramlich V, et al, 1984. Acta Cryst. B. 40:
347.
doi:10.1107/S0108768184002275
http://dx.doi.org/10.1107/S0108768184002275
4. Bagautdinov B, Brown ID, 2000. J. Phys.: Cond. Matt. 12: 8111.
doi:10.1088/0953-8984/12/37/310
http://dx.doi.org/10.1088/0953-8984/12/37/310
5. Kallayev SN, Gladkii VV, Kirikov VA, Kamilov IK, 1990. Ferroelectrics.
106: 299.
6. Vlokh OG, Gribyk VG, Kityk AV, et al, 1990. Cryst. Rep. 35: 1483.
7. Boulesteix C, Yangui B, Ben Salem M, Manolikas C, Amelinckx S, 1986.
J. Physique 47: 461.
8. Roytburd AL, 1993. Phase Trans. 45: 1.
9. Dudnik EF, Shuvalov LA, 1989. Ferroelelectics. 98: 207. |