SUPERCONDUCTING PROPERTIES OF YBA2CU3-XFEXOY CERAMICS WITH SMALL-X

The influence of iron doping on the transition temperature to the supe rconducting state has been studied in ceramic YBa2Cu3-xFexOy (0 less t han or equal to x less than or equal to 0.01) samples by means of AC s usceptibility chi'-i chi'' measurements. A statistical character of th e onset transition temperature to the superconducting state T-c(on) de pending on iron concentration (x) was found. Monotonously decreasing b ehavior for the intergranular weak link coupling temperature T-m(J) de pending on AC magnetic field amplitude it, was observed. The higher th e x the higher the dropping rate of T-m(J) was observed for relatively strong field. It is found that the dropping rate of T-m(J) against x is essentially decreasing in the range 0.003<x<0.007 and again is shar ply reduced for higher x up to 0.01. Possible explanations of obtained results are discussed. (C) 1998 Elsevier Science B.V.