Influence of Metal Diboride and Dy2O3 Additions on Microstructure and Properties of MgB2 Fabricated at High Temperatures and under Pressure

• Published in: Scientific reports 2016-07, Vol.6 (1), p.29306-29306, Article 29306
• Main Authors: Yang, Y., Sumption, M. D., Collings, E. W.
• Format: Article
• Language: English
• Subjects: 639/301/119/1003; 639/638/298/924; High temperature; Humanities and Social Sciences; multidisciplinary; Science
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep29306

High temperatures and under pressure (HTP) processing has been used to study the effects of chemical doping in MgB 2. ZrB 2 , TiB 2 and NbB 2 were selected as additives since, like MgB 2 , they have an AlB 2 -type structure and similar lattice parameters. Dy 2 O 3 was selected as it has been reported to generate nanoscale, secondary intragrain phases in MgB 2 . While C is known to enter the B-sublattice readily, attempts to dope Zr and other elements onto the Mg site have been less successful due to slow bulk diffusion, low solubility in MgB 2 , or both. We have used high-temperature, solid-state sintering (1500 °C), as well as excursions through the peritectic temperature (up to 1700 °C), to investigate both of these limitations. Bulk MgB 2 samples doped with MB 2 (M = Zr, Ti and Nb) and Dy 2 O 3 additions were synthesized and then characterized. Lattice distortion and high densities of crystal defects were observed in the MgB 2 grains around nano-sized MB 2 inclusions, this highly defected band contributed to a large increase in B c2 but was not large enough to increase the irreversibility field. In contrast, distributed intragrain precipitates were formed by Dy 2 O 3 additions which did not change the lattice parameters, T c , T c distribution or B c2 of MgB 2 , but modified the flux pinning.