Preparation of superconductor materials by the roller-splat cooling method

Abstract

The powders of bismuth oxide, strontium carbonate, calcium carbonate and copper oxide taken in the molar ratio 4-3-3-4 are mixed together, then heated up to 1000 °C in a platinum crucible. The melt thus obtained, is quenched by splat cooling method using two twin rollers. The roller's speed is adjusted in order to obtain large amorphous flakes. The crystallization of these amorphous flakes is studied by means of differential thermal analysis (DTA) in order to determine the different heat treatments. Powder X-ray diffraction analysis is performed to identify existing phases in quenched and annealed samples. The morphology of samples is observed using a scanning electron microscope (SEM). Superconductor 4-3-3-4 is obtained after annealing at 800 °C in air, since a superconductive transition is observed at 85 K. Those same synthesis method and analysis techniques are performed to prepare the BaPb 0.75Bi 0.25O 3 superconductor with low critical temperature. The starting mixture melts at 1200 °C and the superconductor crystallizes at about 600 °C. A single superconducting transition is obseved at 11 K.