Optical and Dilatometric Properties of (CH3)2NH2Al(SO4)2·6H2O Crystals in Paraelectric and Ferroelectric Phases |
| D. Podsiadła, Z. Czapla Institute of Experimental Physics, University of Wroclaw, Pl. M. Borna 9, 50-204 Wroclaw, Poland B. Andriyevsky and O. Myshchyshyn Faculty of Physics, Ivan Franko State University of L'viv, 8 Kyryla and Mefodiya Str., 290005 L'viv, Ukraine |
| Received: March 22, 1999 |
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| Experimental investigation of the thermal linear expansion l(T) and temperature dependencies of the interference optical path difference D(T) were carried out for (CH3)2 NH2Al(SO4)2·6H2O crystal, in the range of 120-310 K for three crystal physical directions. Decrease in electrostriction coefficients g of crystal was observed on approaching the phase transition point Tc ≈ 150 K in ferroelectric phase. Relative temperature changes of the lengthening δl/l and refractive index δn/(n-1) are of the same order of magnitude. Peculiarities of temperature dependence of dilatometric and optical parameters of (CH3)2NH2Al(SO4)2·6H2O testify for qualitative reconstruction of chemical bonds in the crystal when temperature changes in the same phase. |
| DOI: 10.12693/APhysPolA.96.409 PACS numbers: 64.70.Kb, 78.20.Fm |