SYNTHESIS, CRYSTAL-STRUCTURE AND MAGNETIC-PROPERTIES OF SUPERCONDUCTING SINGLE-CRYSTALS OF HGBA2CUO4+DELTA

Single crystals of HgBa2CuO4+delta of submillimetric sizes were grown with the same one step, low pressure, gold amalgamation technique used to obtain single crystals of HgBa2Ca2Cu3O8+delta. Remarkable supercon ducting properties are displayed by the samples which are optimally do ped as grown. The sharpness of the transition profiles of the magnetic susceptibility, its anisotropy dependence and the volume fraction exh ibiting the Meissner effect exceed the values obtained with the best c rystal samples of Hg-1223. X-rays show that no substitutional defects have been found in the mercury plane, in particular no mixed occupancy of copper at the mercury site; The interstitial oxygen content at (1/ 2, 1/2, 0) delta = 0.066 +/- 0.008 is about one third that observed in optimally doped Hg-1223, resulting in an identical doping level per C uO2 plane in both compounds.