Phase Transition of Nb[sub.3]Sn during the Heat Treatment of Precursors after Mechanical Alloying

• Published in: Crystals (Basel) 2023-04, Vol.13 (4)
• Main Authors: Sun, Wanshuo, Chen, Shunzhong
• Format: Article
• Language: English
• Subjects: Crystals; Structure; Superconductors
• ISSN: 2073-4352; 2073-4352
• DOI: 10.3390/cryst13040660

The phase transition process of Nb[sub.3]Sn during heat treatment exerts important influences on Nb[sub.3]Sn formation and the superconducting characteristics of Nb[sub.3]Sn superconductors. A simple method for quickly preparing Nb[sub.3]Sn was studied. First, Nb, Sn, and Cu powders were mechanically alloyed to prepare the precursor. Then, the precursor was heat treated at different times to form Nb[sub.3]Sn. During the first stage, the morphology and crystal structure of the products were analyzed after different milling times. The results of the transmission electron microscopy showed the poor crystallinity of the products compared with the original materials. During the second stage, heat treatment was performed at different temperatures ranging from room temperature to 1073 K. After treatment, the products were studied via X-ray diffraction analysis to determine how the structure changed with increasing temperature. Only the Nb diffraction peaks in the precursor were observed after high-energy ball milling for more than 3 h. When the heat treatment temperature was above 773 K and heat treatment time was 15 min, Nb[sub.3]Sn began to form. When the temperature was above 973 K, some impurities, such as Nb[sub.2]O[sub.5], appeared. After 5 h of ball milling, the precursor was heat treated at different times in a vacuum heat treatment furnace. The crystal structure of the product exhibited evident diffraction peaks of Nb[sub.3]Sn. The critical temperatures of the samples that were heat treated at different times were between 17 K and 18 K. The magnetic critical current density of the sample versus the applied magnetic field at 4.2 K indicated that the magnetic J[sub.c] was approximately 30,000 A/cm[sup.2].