Microstructure and Composition Comparison of Ti- and Ta-Doped Nb3Al Superconducting Wires Fabricated by RHQT Process

Herein, the microstructure and composition of the Ti- and Ta-doped Nb3Al superconductor fabricated by rapid heating, quenching, and transformation (RHQT) process are compared. After rapid heating and quenching (RHQ) process, body-centered cubic (bcc) phase is formed in all the wires, showing dark stripe and bright contrast morphology in the backscattered electron (BSE) images. After transformation heat-treatment, all wires consist of A15 phase and show the same morphology as that of the quenched samples. Near-stoichiometric composition is shown in 3 at% Ti- and Ta-doped Nb3Al samples, but when doping amount is 10 at%, Ti-doped sample has constant Nb content of 67 at% and Ta-doped sample has Al + Ta content of 25 at%. Superconducting properties of both 3 at% Ti- and Ta-doped Nb3Al samples are comparable and much superior than that of 10 at% doped samples, including critical temperature (T-c), critical current density (J(c)), and irreversible field (B-irr). Though 10 at% Ta-doped Nb3Al has higher T-c than 10 at% Ti-doped sample, it presents wider Delta T-c value and lower J(c) performance. When increasing the measurement temperature from 8 to 10 K, the decay ratio of B-irr value for Ti-doped Nb3Al superconductor follows the scaling law; however, the Ta-doped samples are not the case.

Automated summary

This study compares the microstructure and composition of Ti- and Ta-doped Nb3Al superconductors fabricated using a rapid heating, quenching, and transformation process. The results show that the 3 at% Ti- and Ta-doped samples exhibit superior superconducting properties compared to the 10 at% doped samples. The Ti-doped sample has a constant Nb content of 67 at% while the Ta-doped sample has an Al + Ta content of 25 at%.