ELASTIC PROPERTIES OF SUPERCONDUCTING PB-(1+X 2)CU-(1-X/2)(SR1-YCAY)(2)(Y1-XCAX)CU2O7+DELTA/

Using a vibrating reed technique, internal friction (Q(-1)) and Young' s-modulus sound velocity (V-E) were measured for polycrystalline sampl es of two types of superconducting Cu0.25(Sr0.5Ca0.1)(2)(Y0.5Ca0.5)Cu2 O7+delta(T-c=58 and 48 K) and insulating Pb0.5Cu0.5Sr2YCu2O7 in the te mperature range between 30 and 300 K. For each of the samples, a broad peak was observed at 180 K in the Q(-1) vs. T curve. For superconduct ing samples, V-E increased monotonically with lowering temperature. Mo reover, there appeared to be a distinct change in slope of V-E(dV(E)/d T) around 230 K. For an insulating sample, as temperature lowered, V-E increased monotonicaly without any obvious change in dV(E)/dT. Furthe rmore, it was found that the temperature dependence of the magnitude o f slope (-dV(E)/dT) was akin to that of Q(-1) for each sample. These b ehaviors were thought to be attributable to collective displacements o f oxygen atoms and/or Pb and Cu atoms in the (Pb,Cu)-O plane.