Study of the Defect Structure and its Influence on the Phononic and Electronic Properties in M1-xVxB2 Superconducting Compounds

• Grant number: 14/25235-3
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: May 01, 2015
• End date: April 30, 2016
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Nonmetallic Materials
• Principal Investigator: Durval Rodrigues Junior
• Grantee: Sérgio Tuan Renosto
• Host Institution: Escola de Engenharia de Lorena (EEL). Universidade de São Paulo (USP). Lorena , SP, Brazil

Abstract

This post-doctoral project deals with the systematic investigation of the defect structure created in doped diborides doped of the M1-xVxB2 type, and its relation to the important changes in the physical properties of the MB2 diboride matrix, leading to superconducting behavior. Recently, it was reported by the candidate that the partial replacement of the metal M (Hf or Zr) by V, Nb or Y in these samples, showed that distortions of the crystal lattice, associated with a defect structure, induce the emergence of the superconducting order parameter in the normal compounds of ZrB2 and HfB2, with Tc of 8.7 and 9.3 K, respectively. In fact, unprecedented measurements of the specific heat, comparing the behavior of samples of ZrB2 and Zr0.96V0.04B2, showed that a small partial replacement generates important changes both in the phonon spectrum and in the density of states. The preliminary results presented in this proposal show that this work is auspicious in the possibility of understanding the superconductivity in a new family of superconducting materials, and refers to the experimental investigation of the physical and structural properties of these diborides, by techniques such as scanning electron microscopy, transmission electron microscopy with electron diffraction, measurements of specific heat, Hall effect, Raman spectroscopy and thermal expansion coefficients. Besides the scientific merit of the project, its development will allow the improvement of the applicant's training, once he will be in contact with important techniques of materials characterization, also consolidating our research group in this important area of knowledge.

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

RENOSTO, S. T.; LANG, R.; DIEZ, E.; CORREA, L. E.; DA LUZ, M. S.; FISK, Z.; MACHADO, A. J. S.. Evidence of unconventional superconductivity in the Ni-doped NbB2 system. Journal of Alloys and Compounds, v. 787, p. 414-422, MAY 30 2019. (18/08819-2, 14/25235-3)