An ultrasonic study of the elastic properties of the normal and superconducting states of YBa₂Cu₃O7-δ

The elastic properties of YBa 2 Cu 3 O 7- delta ceramic have been determined from ultrasonic wave velocity measurements between 5 K and 260 K. In the vicinity of the superconducting transition temperature both longitudinal and shear mode velocities show decreases with temperature, an indication of long-wavelength acoustic mode softening. Below T c the mode velocities increase quite steeply. The elastic stiffness of this material is substantially smaller than that of ideal perovskite materials, a feature which can be abscribed to the oxygen defect, layer-like structure.