Advanced search
Start date
(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Absence of superconductivity in NbB

Full text
Abud, F. [1] ; Correa, L. E. [2] ; Souza Filho, I. R. [2] ; Machado, A. J. S. [2] ; Torikachvili, M. S. [3] ; Jardim, R. F. [1]
Total Authors: 6
[1] Univ Sao Paulo, Inst Fis, Rua Matao 1371, BR-05508090 Sao Paulo, SP - Brazil
[2] Univ Sao Paulo, Escola Engn Lorena, Caixa Postal 116, BR-12600970 Lorena, SP - Brazil
[3] San Diego State Univ, Dept Phys, San Diego, CA 92182 - USA
Total Affiliations: 3
Document type: Journal article
Source: PHYSICAL REVIEW MATERIALS; v. 1, n. 4 SEP 8 2017.
Web of Science Citations: 2

A systematic study of the superconducting properties in a series of arc-melted Nb-B samples close to the 1: 1 composition was carried out. Powder x-ray diffraction (XRD) shows that all samples are both nonstoichiometric and composed of two crystal phases: a majority orthorhombic NbB-type phase and traces of a minor body-centered- cubic Nb-rich phase Nb-ss with stoichiometry close to Nb0.98B0.02. The emergence of superconductivity near T-c similar to 9.0 K was inferred from magnetization data in chunk and powder samples. However, the very small superconducting volume fractions are inconsistent with superconductivity arising from the major NbB phase. On the other hand, micrographs of selected samples clearly show that the minority Nb ss forms a three-dimensional network of filaments that meander around the grains of the majority phase, forming a percolation path. Here we report the superconductivity of the Nb ss phase and argue that the low superconducting volume fraction of nonstoichiometric NbB and zero resistance are due to the filaments of the minority phase. The electronic contribution to the entropy of the superconducting state, yielded from an analysis using the a model for single-band systems, indicates that the Sommerfeld constant of the arc-melted samples is close to the values found in nonsuperconducting NbB. Micrograph, XRD, and bulk measurements of magnetization, electrical resistivity, and specific heat suggest that the superconducting state in the NbB samples bearing some Nb ss minority phase is due to the latter. (AU)

FAPESP's process: 14/19245-6 - Search for novel superconducting materials
Grantee:Renato de Figueiredo Jardim
Support type: Scholarships abroad - Research
FAPESP's process: 13/07296-2 - CDMF - Center for the Development of Functional Materials
Grantee:Elson Longo da Silva
Support type: Research Grants - Research, Innovation and Dissemination Centers - RIDC
FAPESP's process: 14/12401-2 - Superconductivity in (Nb1-xZrx)B solid solutions
Grantee:Fábio Santos Alves Abud
Support type: Scholarships in Brazil - Master