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On the elastic anisotropy of ferroelectric triglycine selenate
Author(s) -
Khanna S. K.
Publication year - 1983
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221160122
Subject(s) - ferroelectricity , condensed matter physics , anisotropy , phase transition , phase (matter) , dipole , landau theory , dielectric , materials science , physics , optics , quantum mechanics
The numerical values of the elastic constants C 11 , C 22 , C 33 , C 15 , C 35 , C 55 are determined experimentally by using an acousto‐optical method. Results are reported of the anisotropy of the velocity of 10 MHz ultrasonic waves in the direct vicinity of the phase transition temperature. It is observed that in the ferroelectric phase the velocity rises with a rotation of the sound wave vector by 2 to 4° with respect to the z ‐axis in the Y–Z plane. On the other hand these critical anomalies of velocity are found to follow an identical logarithmic behaviour in the paraelectric phase. The results are discussed on the basis of Landau theory but at the same time taking into account the long range dipole–dipole interactions as well as the fluctuations of the order parameter. The correlation parameter is estimated from the temperature dependence of the elastic coefficient in the paraelectric phase (δ = 0.2 × 10 −16 cm 2 ).