MICROSTRUCTURE OF THE MELT-TEXTURED BI1.6PB0.4SR2CA2CU3O10 SUPERCONDUCTOR USING SRO AS SUBSTRATE

We have discovered that SrO is a good ''intervening substrate'', in a melt-textured-growth (MTG) process, to be placed between the bulk samp le and crucible to minimize loss of sample mass due to diffusion. The fractured surfaces of the subsequent MTG bulk sample show highly orien ted layers a few mu m thick in regions on a scale of approximate to 10 0 mu m Some of the layers were found to be composed of further thinner parallel layers of approximate to 0.2 mu m Transmission electron micr oscopy observation reveals that fringes representing the c axis of the aligned 2223 crystals appear in many of our film samples of thickness approximate to 70-80 nm. Tangles of dislocations, tweed structure and crosshatched lattice fringes; were discovered. Although a very slow c ooling rate of 0.5 degrees C h(-1) was used during the crystal formati on period, lattice fringes of various directions and structures show u p on 100 nm-100 Angstrom scales. The difference between the microstruc ture of the Bi specimen and that of the Y-class samples is discussed.