Synthesis of high-temperature superconducting ceramics in the Bi(Pb)-Sr-Ca-Cu-O system based on amorphous precursors

Abstract

The paper presents the results of the synthesis of bismuth superconducting ceramics with compositions Bi1.6Pb0.4Sr2Can-1CunOy (n=2, 3, 5) based on amorphous ceramics obtained by ultrafast melt quenching. In order to increase the rate of formation of superconducting compounds, effective devices have been developed for melting and hardening melts under the action of IR radiation. The sample holder was made of platinum. Melting and hardening were carried out in a continuous mode in an oxidizing environment in a flowing air atmosphere. The study of the elemental composition of the precursor samples established a slight deviation towards a decrease in the cationic composition of the precursors (Bi, Pb and Ca), relative to the stoichiometric composition. An increase in oxygen content by 12–15 % was also found. Synthesis of superconducting compounds was carried out in the temperature range of 843–850 °C, depending on the composition. The study found that in the sample Bi1.6Pb0.4Sr2Ca4Cu5Oy (2245) the superconducting high-temperature phase 2223 crystallizes. It was found that the formation of the superconducting phase 2223 in the Bi1.6Pb0.4Sr2Ca4Cu5Oy composition occurs in a lower and wider temperature range (843–848 °C) compared to the Bi1.6Pb0.4Sr2Ca2Cu3Oy (2223) composition. The complete formation of the superconducting high-temperature phase 2223 in a sample with the nominal composition Bi1.6Pb0.4Sr2Ca2Cu3Oy (2223) was carried out in a narrow temperature range of 849–850 °C, in a strict temperature regime with the participation of the liquid phase. An increase in the rate of formation of the superconducting compound 2223 in both studied compositions by 1.5–2.5 times was established, compared with the solid-phase method and other melt methods