On the Road to Practical, Low-cost Superconductors with Unexplored Materials

Superconductors have tremendous appeal in power transmission applications due to their zero resistance. However, to bring classical metallic superconductors into superconducting state requires liquid helium as a coolant, which is costly. Now, scientists from Miryala Lab take things to the new level by demonstrating high temperature superconductivity in mixed rare-earth barium copper oxides fabricated using a popular technique, opening doors to their low-cost, industrial scale production for real-world applications.

Among the several techniques available for fabricating bulk RE-123, the team went for an infiltrated growth (IG) technique, in which solid (RE)BaCuO5 (RE-211) reacts with a Ba-Cu-O liquid phase to form the superconducting RE-123. Prof. Miryala lays down the motivation behind their approach: “IG technique produces RE-123 bulks without homogeneities, can be performed in air, and scaled up to industrial levels. Moreover, it provides a fertile ground for exploring ternary RE elements systems, which have not been studied until now”.

Recently, the team investigated the ternary (Gd0.33Y0.33-xEr0.33+x)-123 bulk system, optimizing its composition by tuning the ratio of Y and Er in the 211 precursor (specifically, x = 0, 0.05, 0.1, 0.15, and 0.2). The XRD proved the single-crystalline nature of the RE-123 bulks, with Tc values in the range (91.5-92) K, significantly above boiling point of liquid nitrogen (77K), and the highest trapped field of 0.61 tesla in (Gd0.33Y0.13Er0.53)-123 (x=0.2) sample with 20 mm in diameter and 7 mm in thick. FESEM and EDX identified finely dispersed (Gd, Y, Er) -211 particles in all samples, with an Er-rich precipitates distribution for x=0.2, the sample which also showed the best superconducting performance.

Trapped field values under applied fields of 1 and 0.5 T  at 77K as a function of x for (Gd0.33Y0.33-xEr0.33+x)-123 samples (left). After maximum external field application, this field is switched off but part of stays trapped in the superconducting bulk, making of it a powerful permanent magnet (right).

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