Attenuation of low-frequency elastic oscillations in ferroelastic KH 3 (SeO 3 ) 2

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Abstract
Temperature dependences of internal friction Q −1 and shear modulus G at the frequency of ∼ 1 c/s of KH3(SeO3)2 crystals were studied by torsion pendulum technique in the temperature range from −190°C to+50°C. Two peaks were found on the Q −1(T) curves, the first in the vicinity of Tc and the second at −150°C related to the phase transition and loss domain mechanism respectively. The measurements show that below Tc Q −1(T) and G(T) the behaviour considerably depends on domain structure state. Shear elastic stiffnesses c 44, c 55 and c 66 above Tc have been calculated from experimentally found Gx , G y and G x . It was clarified that c 55 tends to zero when T ← T c . The basic experimental results are discussed in terms of phenomenological theory.