FLUORINATION OF UNDERDOPED MERCUROCUPRATE SUPERCONDUCTORS

We present the results of a study into the incorporation of fluorine i nto the mercurocuprate superconductors. In all cases, the effect of fl uorination has been to increase the (T)c of underdoped superconductors to the maxima reported. This has important ramifications for the role of the interstitial oxygen in the mercurocuprate superconductors. To assist us in our study, we have, additionally, developed a novel synth etic procedure for preparing HgBa2CuO4+delta in a highly underdoped st ate. Remarkably, this material shows an increase in T-c, upon fluorina tion, of 60K!.