Effects of Quenching and Sintering Temperature on Ultrasonic Attenuation in GdBaSrCu3O7-δ HIGH-Tc Superconductors

Ultrasonic longitudinal and shear attenuation measurements was performed at 5-10 MHz in superconducting GdBaSrCu₃O_7-δ between 80 K and 285 K. Longitudinal attenuation profiles showed a large peak around 215 K for low-temperature annealed GdBaSrCu₃O_7-δ but not for quenched GdBaSrCu₃O_7-δ. A smaller peak was also observed at the same temperature for high-temperature annealed GdBaSrCu₃O_7-δ. It is suggested that the differences in the attenuation profiles are due to oxygen O(4) and O(5) ordering involving Cu-O chains of the materials.