Processing, Characterisation and Properties of the Superconducting Tl-Ba-Ca-Cu-O System
The Tl-Ba-Ca-Cu-O system, when prepared by standard sintering procedures, shows mass loss by volatilisation of Tl even at sintering temperatures lower than the decomposition temperature of Tl2O3 (850°C). The disappearance of Tl results in difficulties in preparation, especially since Tl2O3 emission is severely toxic. The use of a two-stage sintering technique involves first the preparation of Ba-Ca-Cu-O by standard ceramic processing, so that TI2O3 can be added to the sintered Ba-Ca-Cu-0, enclosed in a silver tube, and sintered. This technique ensures reproducible results and safety. Two superconducting phases were confirmed by Tc measurements, x-ray diffraction patterns, and electron microanalysis. The materials were characterised by DTA, electrical and magnetic measurement, and TEM. Prolonged sintering degraded the superconducting properties, probably due to thallium evolution. Transition broadening in applied magnetic fields is ascribed to anisotropy.
KeywordsDifferential Thermal Analysis Superconducting Property Meissner Effect Super Lattice Tetragonal Unit Cell
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