Dehydrogenation-induced crystal defects for significant enhancement of critical current density in polycrystalline H-doped MgB2

• Published in: Journal of materials science. Materials in electronics 2021, Vol.32 (1), p.843-852
• Main Authors: Cai, Qi, Li, Xinyao, Li, Shukui, He, Chuan, Liu, Xingwei, Feng, Xinya
• Format: Article
• Language: English
• Subjects: Borohydrides; Characterization and Evaluation of Materials; Chemistry and Materials Science; Critical current density; Crystal defects; Dehydrogenation; Magnesium compounds; Materials Science; Optical and Electronic Materials; Pinning; Transition temperature
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-020-04862-x

The present study discovers the significant enhancement of critical current density by the pinning of borohydride and crystal defects in the hydrogen-treated MgB 2 bulks. Based on the concept of gas doping, the nanosized borohydride Mg(BH 4 ) 2 is formed by synthesizing H-doped MgB 2 bulks in an H 2 atmosphere at 300 °C and 350 °C, and the critical current density was enhanced over the entire field. The H-doped MgB 2 bulks are then experienced dehydrogenation at 300 °C and 350 °C, respectively, and the decomposition of Mg(BH 4 ) 2 induced nanosized pits on the surface of the MgB 2 grains, leading to a further enhancement of critical current density, 1.5 × 10 4 A cm −2 at 20 K and 2.5 T, which is three times larger than that of the un-doped MgB 2 sample, 4.8 × 10 3 A cm −2 . The hydrogenation and dehydrogenation hardly changed the superconducting transition temperature or the pinning mechanism of the MgB 2 samples. The enhancement of the critical current density is possibly attributed to the pinning effects of the crystal defects, and the reduction of MgO.