ULTRASONIC VELOCITY STUDIES ON SUPERCONDUCTING AND NONSUPERCONDUCTINGERBA2CU3O7-DELTA

The shear ultrasonic velocity of single-phase polycrystalline supercon ducting (orthorhombic) and non-superconducting (tetragonal) samples of ErBa2Cu3O7-delta has been determined from 80 to 210 K using the pulse -echo-overlap ultrasonic method at 10 MHz. The absolute shear velocity decreased when the oxygen content was reduced from O-6.92 to O-6.25. An elastic anomaly was observed just below 200 K in the superconductin g but not in the non-superconducting sample. No difference in the grai n size and porosity of both samples was observed and the elastic behav ior was explained in terms of the different oxygen contents. The acous tic Debye temperature of the superconducting sample in the void-free a pproximation was estimated to be Theta(D) similar to 480 K.