MICROSTRUCTURE AND PHASE-COMPOSITION OF HG-1223 BULK PHASE SUPERCONDUCTORS

The superconducting HgPb0.4Ba2Ca2Cu3Oy 1223 phase was prepared by a mi xed oxide technique and by solid state reactions. The resistance measu rements yielded T-c(0)-values of 126 K with transition widths of 4 K. X-ray diffraction confirmed the presence of the superconducting 1223 p hase. Scanning electron microscopy in combination with EDX showed that besides the superconducting crystallites, BaCuO2, CaO, CuO, BaPbO3 as well as BaCO3 and BaO and CaO mixtures and CaHgO2 were present as sec ondary phases. High-resolution optical microscopy in normal and polari zed Light yielded information on the porosity and the distribution of the superconducting and the secondary phases. (C) 1998 Elsevier Scienc e B.V. All rights reserved.