An ultrasonic study of energy-gap and granular characteristics of Y1Ba2Cu3O7-ysuperconducting ceramic

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Abstract
Ultrasonic attenuation measurements of Y1Ba2Cu3O7-y have been carried out between 100 and 10 K by using 10-25 MHz longitudinal acoustic waves. It was shown from the experimental results that when Tc the attenuation was apparently decreased and the granular superconducting characteristics of the samples were remarkable. It was indicated from the attenuation curves that the superconductivity of Y1Ba2Cu3O7-y is related to the electron pairing states. By means of introducing a transition volume distribution function fT, the calculated attenuation curves fitted the experimental ones very well, leading to a result of 2 Delta (0)=3.5kBTc. This suggests that the existence of a superconducting energy gap and its temperature dependence should be still the same with the BCS theory, although the mechanism of the electron coupling may be quite different.