Award Date

8-1-2016

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Physics and Astronomy

First Committee Member

Andrew Cornelius

Second Committee Member

Ravhi Kumar

Third Committee Member

Michael Pravica

Fourth Committee Member

Thomas Hartmann

Number of Pages

50

Abstract

Niobium chalcogenide compounds have recently gained a great deal of interest due to the fact that a superconducting phase coexists with the charge density wave state (CDW), as well as their potential for numerous applications. Two superconducting compositions, NbSexTe2-x (x=2, 1.5) were prepared by solid state route using high purity Nb, Se, and Te powders. Powder X-ray diffraction patterns collected at ambient conditions for NbSe2 and NbSe1.5Te0.5 showed a single phase with hexagonal crystal structure, with space group P63mmc. High-pressure X-ray diffraction measurements were performed at the Advanced Photon Source at Argonne National Laboratory to investigate structural stability up to 39 GPa. The bulk moduli were found to be 52 GPa for NbSe2 and 61.7 GPa for NbSe1.5Te0.5 respectively. No pressure induced phase transitions were observed within the studied pressure range. Tc at ambient pressure was determined to be 7.1 K and 3.35 K for NbSe2 and NbSe1.5Te0.5 correspondingly. As a superconducting transition was measured under high pressure for NbSe1.5Te0.5 . A positive pressure dependence was observed, with the critical temperature increasing from 3.35 K at ambient, to 4.4 K at 1.8 GPa, at a rate of 0.6 K/GPa.

Disciplines

Physical Chemistry | Physics | Science and Mathematics Education

Language

English


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