Structural phase evolution and superconductivity in the non-stoichiometric intermetallic compound niobium diboride

Zhi An Ren; Sogo Kuroiwa; Yoko Tomita; Jun Akimitsu

doi:10.1016/j.physc.2008.01.001

Structural phase evolution and superconductivity in the non-stoichiometric intermetallic compound niobium diboride

Zhi An Ren, Sogo Kuroiwa, Yoko Tomita, Jun Akimitsu

Research output: Contribution to journal › Article › peer-review

17 Citations (Scopus)

Abstract

The structural changes and superconductivity in the layered non-stoichiometric niobium diboride compound were systematically studied for both of niobium-deficient and boron-deficient phases by X-ray diffraction analysis and magnetic susceptibility measurements. The niobium and boron vacancies were found to have different effects on the crystal lattice parameters and superconducting properties; superconductivity only exists in niobium-deficient phases with a clear enhancement of inner-plane B-B bonding and the increase of inter-plane distance, while boron vacancies have the opposite effect of enhancing the Nb-B bonding and breaking the superconductivity. A main superconducting phase with Nb_0.83B₂ composition was obtained with T_c ∼ 9.3-9.9 K, and a = 3.102(1) Å and c = 3.322(2) Å under the optimum sintering conditions. The low temperature specific heat was measured for three high-pressure synthesized superconducting samples to reveal the origin the increase of T_c with the niobium deficiencies.

Original language	English
Pages (from-to)	411-416
Number of pages	6
Journal	Physica C: Superconductivity and its applications
Volume	468
Issue number	5
DOIs	https://doi.org/10.1016/j.physc.2008.01.001
Publication status	Published - Mar 1 2008
Externally published	Yes

Keywords

Niobium diboride
Non-stoichiometric phase
Specific heat
Superconductivity

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Condensed Matter Physics
Energy Engineering and Power Technology
Electrical and Electronic Engineering

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10.1016/j.physc.2008.01.001

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title = "Structural phase evolution and superconductivity in the non-stoichiometric intermetallic compound niobium diboride",

abstract = "The structural changes and superconductivity in the layered non-stoichiometric niobium diboride compound were systematically studied for both of niobium-deficient and boron-deficient phases by X-ray diffraction analysis and magnetic susceptibility measurements. The niobium and boron vacancies were found to have different effects on the crystal lattice parameters and superconducting properties; superconductivity only exists in niobium-deficient phases with a clear enhancement of inner-plane B-B bonding and the increase of inter-plane distance, while boron vacancies have the opposite effect of enhancing the Nb-B bonding and breaking the superconductivity. A main superconducting phase with Nb0.83B2 composition was obtained with Tc ∼ 9.3-9.9 K, and a = 3.102(1) {\AA} and c = 3.322(2) {\AA} under the optimum sintering conditions. The low temperature specific heat was measured for three high-pressure synthesized superconducting samples to reveal the origin the increase of Tc with the niobium deficiencies.",

keywords = "Niobium diboride, Non-stoichiometric phase, Specific heat, Superconductivity",

author = "Ren, {Zhi An} and Sogo Kuroiwa and Yoko Tomita and Jun Akimitsu",

note = "Funding Information: This work was supported by the 21st century COE program, “High-Tech Research Center” Project for Private Universities: matching fund subsidy from Ministry of Education, Culture, Sports, Science and Technology (MEXT), and a Grand-in-Aid for Scientific Research on Priority Area from MEXT.",

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AU - Ren, Zhi An

AU - Kuroiwa, Sogo

AU - Tomita, Yoko

AU - Akimitsu, Jun

N1 - Funding Information: This work was supported by the 21st century COE program, “High-Tech Research Center” Project for Private Universities: matching fund subsidy from Ministry of Education, Culture, Sports, Science and Technology (MEXT), and a Grand-in-Aid for Scientific Research on Priority Area from MEXT.

PY - 2008/3/1

Y1 - 2008/3/1

N2 - The structural changes and superconductivity in the layered non-stoichiometric niobium diboride compound were systematically studied for both of niobium-deficient and boron-deficient phases by X-ray diffraction analysis and magnetic susceptibility measurements. The niobium and boron vacancies were found to have different effects on the crystal lattice parameters and superconducting properties; superconductivity only exists in niobium-deficient phases with a clear enhancement of inner-plane B-B bonding and the increase of inter-plane distance, while boron vacancies have the opposite effect of enhancing the Nb-B bonding and breaking the superconductivity. A main superconducting phase with Nb0.83B2 composition was obtained with Tc ∼ 9.3-9.9 K, and a = 3.102(1) Å and c = 3.322(2) Å under the optimum sintering conditions. The low temperature specific heat was measured for three high-pressure synthesized superconducting samples to reveal the origin the increase of Tc with the niobium deficiencies.

AB - The structural changes and superconductivity in the layered non-stoichiometric niobium diboride compound were systematically studied for both of niobium-deficient and boron-deficient phases by X-ray diffraction analysis and magnetic susceptibility measurements. The niobium and boron vacancies were found to have different effects on the crystal lattice parameters and superconducting properties; superconductivity only exists in niobium-deficient phases with a clear enhancement of inner-plane B-B bonding and the increase of inter-plane distance, while boron vacancies have the opposite effect of enhancing the Nb-B bonding and breaking the superconductivity. A main superconducting phase with Nb0.83B2 composition was obtained with Tc ∼ 9.3-9.9 K, and a = 3.102(1) Å and c = 3.322(2) Å under the optimum sintering conditions. The low temperature specific heat was measured for three high-pressure synthesized superconducting samples to reveal the origin the increase of Tc with the niobium deficiencies.

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KW - Specific heat

KW - Superconductivity

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Structural phase evolution and superconductivity in the non-stoichiometric intermetallic compound niobium diboride

Abstract

Keywords

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