SYNTHESIS OF BIBASED HIGH-TEMPERATURE SUPERCONDUCTORS USING MELT TECHNOLOGIES

To obtain high J(c) Bi-based superconducting materials melt-texture te chniques were applied. Amorphous precursors were prepared by rapid que nching (cooling rate about 10(3)-degrees-C/s) of melted powders. Chemi cal composition and preparing routes of the starting mixtures were var ied. The precursor with starting composition Pb0.2Bi1.8Ca1Sr2Cu2O8 was chosen among others for further investigations because of a maximal c ontent of amorphous phase in it. The sample was crystallized by zone m elting and gradient treatment. The dependence of texture extent on sam ple feeding was stated. The transition from isometric to directional c rystallization at the cooling rate about 10-degrees-C/min was found. T he samples demonstrated J(c) values about 6.10(4) A/cm2 (4.2 K, H = 0 T). Some amorphous impurities on grain boundaries were found by TEM in these samples. One can assume that high J(c) values were reached due to a good grain alignment but not to a grain boundary purification.