EFFECTS OF QUENCHING AND SINTERING TEMPERATURE ON ULTRASONIC ATTENUATION IN GdBaSrCu₃O_7−δ HIGH-T_c SUPERCONDUCTORS

Abstract

Ultrasonic longitudinal and shear attenuation measurements was performed at 5-10 MHz in superconducting GdBaSrCu 3 0 7 .,s between 80 K and 285 K. Longitudinal attenuation profiles showed a large peak around 215 K for low-temperature annealed GdBaSrCu 3 0 7 .,s but not for quenched GdBaSrCu 3 0 7 .* A smaller peak was also observed at the same temperature for hightemperature annealed GdBaSrCu 3 0 7 .* It is suggested that the differences in the attenuation profiles are due to oxygen 0(4) and 0(5) ordering involving Cu-O chains of the materials.