Sol-gel preparation and characterization of manganese-substituted superconducting YBa2(Cu1-xMnx)4O8 compounds

The effect of replacing Cu by Mn on the structural and superconducting properties of YBa2Cu4O8 (Y-124) was studied. Multimetallic oxide powders with the composition YBa2(Cu1-xMnx)4O8 (x = 0.00, 0.01, 0.02, 0.03, 0.04 and 0.05) were prepared by a simple aqueous sol-gel method at an oxygen pressure of 1 atm starting from an aqueous mixture of the metal acetates. Homogeneous gels were achieved by complexing copper ions by tartaric acid before the gelation process. Thermal decomposition of the gels was studied by TG. The effect of Mn substitutions on the properties were studied by XRD, TG, IR spectroscopy and resistivity measurements. These data showed that the critical temperature drastically decreased upon Mn substitution, and that superconductivity is lost at 3% Mn. XRD showed that the structure of the Y-124 phase is also largely affected, even at low Mn levels. 42 refs.