LOW-TEMPERATURE MECHANICAL ENERGY-DISSIPATION PHENOMENA IN PRASEODYMIUM-DOPED YTTRIUM SUPERCONDUCTORS

Studies of the anelastic properties of Y1-xPrxBa2Cu3O7-delta ceramics (0 less than or equal to x less than or equal to 1) were performed. Th e internal friction and Young modulus measurements were carried out by the vibrating reed technique in the temperature range from 20 to 180 K. The measurement frequency was in the range 90-760 Hz. The aim of th is work was to investigate the influence of praseodymium content on th e anelastic properties of 1-2-3 material. The main phenomena which are caused by doping with praseodymium can be seen in the low temperature part of the internal friction spectra (20-40 K). The maximum at about 40 K, known as maximum 1 in the spectra of yttrium 1-2-3 material, gr adually decreases with increasing praseodymium content. Relaxation pro cesses located in the conducting planes, possibly electronic phenomena , have been considered as an origin of maximum 1. The samples which co ntained more than 50% Pr showed another low temperature maximum 25-30 K. This maximum also reflects thermally activated relaxation phenomena . Its estimated activation energy is very low (0.03 eV). The common fe ature of all the Y1-xPrxBa2Cu3O7-delta samples regardless of the dopan t content is the presence of internal friction maxima observed in our frequency range at 80 and 100 K (maxima 3 and 4 in the spectra of 1-2- 3 material). These processes were not significantly affected by the pr esence of praseodymium.