SIMULTANEOUS PYROELECTRIC AND DILATOMETRIC STUDIES OF PHASE TRANSITIONS IN TRIGLYCINE SULPHATE AND GLYCINE PHOSPHITE CRYSTALS
B. Andriyevsky, V. Kardash
The Ivan Franko National University of L'viv, 8 Kyrylo & Mefodii Str., 79005 L'viv, Ukraine
S. Dacko and Z. Czapla
Institute of Experimental Physics, University of Wroc³aw, 9 M. Born Sqr., 50-204 Wroc³aw, Poland
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Received: November 3, 2000; revised version February 5, 2001
Temperature dependences of the linear dimension L(T) and spontaneous polarization Ps(T) for triglycine sulphate and glycine phosphite single crystals have been measured in the same run of temperature. A decrease in the spontaneous electrostriction coefficient QL of both crystals studied is displayed when approaching the corresponding phase transition point Tc. A temperature dependence of the coefficients QL(T) shows that the rates of temperature changes of displacement of the atomic complexes of corresponding crystal structure forming the square of spontaneous polarization Ps2 (primary order parameter) and the displacements of all atomic complexes forming the spontaneous linear thermal expansion δLs/L (secondary order parameter) are different. The applying external electric field E=3×105 V/m to triglycine sulphate crystal does not influence essentially the temperature dependence of QL(T) in the temperature range of phase transition below Tc.
DOI: 10.12693/APhysPolA.99.593
PACS numbers: 77.80.Bh