Abstract
Longitudinal and transverse sound velocity and attenuation measurements as a function of temperature (4.2–280 K) and frequency (3–30 MHz) have been carried out in compounds of the type YBaCuO and Bi,PbSrCaCuO. The elastic properties of the ceramic samples, characterized by bulk modulus and Poisson ratios, are strongly affected by the microstructure (grain size, density) and the oxygen stoichiometry; YBa 2Cu 3O 7 − δ samples of different δ values have different Poisson ratios ( ν ortho < ν tetra ). Anelastic processes in the absorption were found in orthorhombic and tetragonal YBaCuO samples. A single thermally activated Debye process was observed with an activation energy H = 90 meV and an attempt frequency ν 0≈ 10 11 Hz. This was derived from the line width of the absorption peaks and the shift of the absorption maximum with frequency.
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