Sound Velocity, Attenuation and Thermal Contraction in the High T sub c Superconductor La sub 1.85 Sr sub .15 CuO sub 4

The sound velocity and attenuation near 10 MHz have been measured on a sintered sample of La sub 2.85 Sr sub .15 cuO sub 4. The sound was generated with standard lithium niobate transducers and measured with pulsed phase mixing technique. The sample had a transition temperature of 43 K and width of 0.5 K as determined from a.c. susceptibility. The thermal contraction of the sample was measured to correct the sound velocity, and showed a break at 200 K, indicating the tetagonal to orthohombic phase transition.