Processing of bulk Bi-2223 high-temperature superconductor

Abstract

The Bi2Sr2Ca2Cu3 O10+x (Bi-2223) is one of the main high temperature superconductors for applications. One of these applications is the Superconductor Fault Current Limiter (SCFCL), which is a very promising high temperature superconducting device. SCFCL's can be improved by using bulk superconductors with high critical currents, which requires a sufficiently dense and textured material. In the present work, a process for improving the microstructure of Bi-2223 bulk samples is investigated. Pressed precursor blocks are processed by sintering with a further partial melting step, in order to enhance the Bi-2223 grain texture and to healing cracks induced by pressing. In order to improve the microstructure, the precursor is mixed with silver powder before pressing. Samples with and without silver powder have been studied, with the aim of investigating the influence of silver on the microstructure evolution. The phase contents and the microstructure obtained have been analyzed through XRD and SEM/EDS. The electromagnetic characterization has been performed by Magnetic Susceptibility Analysis. We present and discuss the process and the properties of the superconducting blocks. High fractions of textured Bi-2223 grains have been obtained

Predictable and robust performance of a Bi-2223 superconducting coil for compact isochronous cyclotrons

“…Cooldown took approximately three days before reaching the final temperature of about 20 K. During cool-down, the temperature sensors on the coil stayed within ±1 K. The normal to superconducting transition is 108 K, as can be derived from figure 4, in which the voltage is plotted as a function of the average temperature of the coil. The measured transition is in good agreement with the critical temperature found in the literature [13,14].…”

Excess Conductivity Analyses in Bi-Pb-Sr-Ca-Cu-O Systems Sintered at Different Temperatures

“…The hole concentration on the CuO2 plane is determined by the following formula [21]: Through the data from Table 1, it is clearly seen that increasing the sintering temperature directly affects Tc and p. The Tc of the sample gradually increases from 90.02 K for M0_835 sample to 109.38 K for M0_850 sample. These results are in good agreement with the Tc of the samples given in previous studies [5,7,8,20]. It has been widely reported in the literature that Tc of Bi-2212 phase is 80 K and that of Bi-2223 phase is 110 K. The obtained values of Tc might reveal the co-existence of the two superconducting phases Bi-2212 and Bi-2223 in our samples.…”

“…It is observed that the four samples consisted of two superconducting phases: Bi-2212 (marked as "L") and Bi-2223 (marked as "H"). In addition, the presence of secondary Ca2PbO4 phase (marked as "+") has been attributed to the result of partial reaction between Pb with other precursors during sample fabrication [7][8][9][10]. The Ca2PbO4 phase plays an important role in accelerating the formation of Bi-2223 phase [7,10].…”

“…The previous studies pointed out that partial substitutions of Pb at the Bi site in the crystal structure might help to reduce the sintering temperature and time. The appearance of Ca2PbO4 was believed to be a reason for enhancing the formation and stabilization of Bi-2223 phase [7][8][9]. Many studies showed that the optimal content ratio of Bi:Pb for the formation of Bi-2223 phase was 1.6:0.4 [10].…”

“…In this work, we will apply these two models to investigate the excess conductivity as well as the dependence of superconductivity on the sintering temperatures of the four pure Bi1.6Pb0.4Sr2Ca2Cu3O10+δ superconductors sintered at four different temperatures. These temperatures were chosen as sintering temperature due to the fact that the melting point of the system is 855 o C and the formation of Bi-2212 phase is 820 o C [8]. The optimal sintering temperature for the fabrication of the BPSCCO sample with a high-volume fraction of the Bi-2223 phase will be investigated.…”