IRON SUBSTITUTION EFFECTS IN YBA2CU4O8 SYNTHESIZED BY THE SOL-GEL TECHNIQUE

Bulk YBa2((Cu1-yFey)-Fe-57)(4)O-8 samples with y = 0.00-0.05 were synt hesized by an aqueous sol-gel method under 1 atm oxygen pressure. The samples were characterized by XRD for phase purity and lattice paramet ers, by thermal analysis for oxygen stability as well as by magnetic s usceptibility and SQUID, measurements for magnetic and superconducting properties, Iron was found to both destabilize the YBa2Cu4O8 phase an d have a strong effect on its properties even at very low concentratio ns. The site assignment proposed for the iron dopant is based on the r esults of Fe-57 Mossbauer spectroscopy studies. The results are compar ed with the observed iron doping effects in the YBa2Cu3O7-delta phase.