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The NbB2-phase revisited: Homogeneity range, defect structure, superconductivity by Carlos Angelo Nunes; Dariusz Kaczorowski; Peter Rogl; Márcia Regina Baldissera; Paulo Atsushi Suzuki; Gilberto Carvalho Coelho; Andriy Grytsiv; Gilles André; Francoise Boureé; Shigeru Okada is a Engineering article available to read on EtoBox.

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The discovery of superconductivity below 40 K in MgB 2 has motivated new investigations on similar compounds, especially on binary diborides. The great majority of these compounds represent the AlB 2 -type structure (P6/mmm space group, number 191) and comprise line compounds. However, among those, NbB 2 and TaB 2 are reported to present a significant homogeneity region, a value of 12 at.% being reported for the case of NbB 2 . In this work we have evaluated the homogeneity range of the NbB 2 -phase through detailed microstructural characterization of as-cast, as-cast + heat-treated and solid state sintered Nb-B alloys. Neutron diffraction experiments were performed to assess the defect mechanism responsible for accommodating the non-ideal NbB 2 stoichiometries (ideal = 66.7 at.% B). The results clearly showed that the width of the homogeneity range of this phase is nearly 5 at.%, extending from 65 at.% B (NbB 1.86 ) up to 70 at.% B (NbB 2.34 ). Rietveld refinement of the neutron intensity diffraction data indicated a random distribution of vacancies in the Nb-subnet for hyperstoichiometric NbB 2 . The occurrence of a possible Nb-vacancy ordered supercell was evaluated; however, a

Who reads The NbB2-phase revisited: Homogeneity range, defect structure, superconductivity?

Author

Carlos Angelo Nunes; Dariusz Kaczorowski; Peter Rogl; Márcia Regina Baldissera; Paulo Atsushi Suzuki; Gilberto Carvalho Coelho; Andriy Grytsiv; Gilles André; Francoise Boureé; Shigeru Okada

Publisher

Elsevier Science; Elsevier ; Elsevier BV (ISSN 1359-6454)

Published

2005

Language

EN

Field

Engineering (Physical Sciences)