Activation parameters of low-temperature peak of internal friction in YBa2Cu3O7–<i>x</i> ceramics

Temperature dependences of the velocity and absorption coefficient of longitudinal ultrasound with two frequencies f1 = 1.25 × 105 s−1 and f2 = 75 × 105 s−1 are investigated in the temperature interval between 6 and 300 K. Hysteresis of sound velocity under thermal cycling and a series of absorption peaks are recorded. The behavior of the peak localized in the hysteresis region upon a variation of acoustic frequency is analyzed in detail. It is suggested that this peak is associated with a certain thermally activated structural process, and the activation parameters of the process are calculated.

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