THE MECHANICAL AND STRUCTURAL-PROPERTIES OF Y1BA2CU3O7-X SUPERCONDUCTORS

Mechanical losses spectroscopy of two superconducting Y1Ba2Cu3O7-x sam ples (T-c = 93 K) measured at 5, 10, 20 and 30 MHz revealed four peaks . As the frequency of measurement was increased, the peaks shifted to higher temperatures. The relaxation process was found to have an activ ation enthalpy of 0.188, 0.092, 0.209 and 0.314 eV with an attempt fre quency, f(o), equal to 2.46 x 10(15), 5.95 x 10(10), 1.64 x 10(14), an d 7.82 x 10(13) Hz for P-1, P-2, P-3 and P-4 peaks, respectively. The mechanism responsible for these relaxation peaks is discussed. The inf rared spectra of some of these compounds provide evidence for oxygen r earrangement on going from tetragonal to orthorhombic phase. X-ray dif fraction analysis shows that these compounds correspond to a single ph ase which is an orthorhombic perovskite structure.