THE BORDONI RELAXATION IN HIGH-PURITY COPPER SINGLE-CRYSTALS AT LOW-FREQUENCIES

The aim of this work is to explore the low-frequency spectrum of 5N pu re copper in a subresonant pendulum which allows ''in situ'' cycled to rsion deformation and recovery. Samples were taken from the same singl e crystals used for ultrasonic attenuation studies in order to compare both results in an Arrhenius plot. In one sample prepared by electro- erosion, polished with nitric acid, recovered 4 hours at 650 degrees C in preliminary vacuum and 1, 4 and 9% deformed at room temperature, t he spectra show a main Bordoni peak whose height increases with deform ation, and additional peaks in the 40-65K range, as important as the B ordoni peak, which are due to impurities generated during the preparat ion of the sample. In an uncontaminated sample cut by diamond disk, po lished with a mixture of nitric, phosphoric and glacial acetic acids, and water, recovered in 5.10(6) mmHg vacuum, deformed 3 and 5%, the in ternal friction spectra show the main Bordoni peak as the principal ef fect, accompanied by a defect modulus. The study of the influence of d ifferent parameters such as the amount of deformation, the amplitude a nd frequency of oscillation, the temperature rate and the recoveries m ay be an interesting contribution to the characterization of the Bordo ni peak.