THE BORDONI PEAK IN SILVER SINGLE-CRYSTALS AT MEGAHERTZ FREQUENCIES

The dislocation relaxation maximum has been investigated at frequencies of 5, 10 and 30 MHz. The three (very high-purity) silver crystals of crystallographic orientation [111], [110] and [100] which are given a resolved shear stress of 20 MPa were found to produce dislocation relaxation maximum at 107 K in all the three samples. The maximum shifts to 117 K when measurement is carried out at 10 MHz and to 127 K at 30 MHz. The results reveal that the maximum is orientation independent. The activation energy and the attempt frequency were calculated and found to be equal to 0.105 eV and 2 . 10(9) Hz, respectively. Meanwhile the larger magnitude of the maximum was found on the [111] crystal and the least was on the [100] crystal. Finally, it was clearly shown that the dislocation relaxation strength decreases as the frequency increases.