Comparison of the acoustic properties of CuO and YBa2Cu3O<i>x</i> ceramics in the temperature range 5–310 K

Absorption and velocity of ultrasound were compared in samples of the ceramics CuO and YBa2Cu3Ox (x = 6.95 and 6.3) in the temperature range 5–310 K and frequency range 47–370 kHz. The temperature spectra of the ultrasonic absorption in CuO and YBa2Cu3Ox ceramics in the intervals 30–60 and 235–250 K are qualitatively similar; they contain peaks P1 and P4, whose behavior as a function of the frequency of the oscillations is the same for both compounds. The largest differences in the ultrasonic absorption spectra in CuO and YBa2Cu3Ox are observed in the temperature range 100–200 K. The peaks P2 and P3, which are characteristic for the ceramic YBa2Cu3Ox, are not present in the spectrum of CuO ceramic. The temperature dependences of the sound velocity in the ceramic CuO were investigated for the first time and hysteresis under thermal cycling, similar to the hysteresis observed previously in YBa2Cu3Ox, was observed. The existence of hysteresis in CuO as well as in the tetragonal samples of YBa2Cu3Ox is inconsistent with the supposed twinning nature of this material. Evidently, a phase transition occurs and the hysteresis is caused by the development of domain strucutre in the low-temperature phase.

Перевод пока недоступен