PVDF-transducers for MHz-sound attenuation measurements in metals at low temperatures

Piezoelectric PVDF-foils have been tested as transducers for pulse-echo sound attenuation measurements at 10–200 MHz between 4 and 300 K. Their performance is compared with quartz transducers. Measurements of dislocation resonance absorption in high purity copper single crystals are used to demonstrate that the thin foil PVDF transducers in contrast to quartz transducers, during cooling to low temperatures, cause no measurable dislocation effects due to thermal expansion mismatch between sample and transducer. However, measurements of the frequency dependence of attenuation show that foil resonance and foil-λ/4-interference effects have to be carefully considered with respect to measurements of stress amplitude-, frequency- and temperature-dependence of attenuation.