Superconductivity and phase stability of Nb/sub 3/Ge

Journal Article · Wed Sep 01 00:00:00 EDT 1976 · J. Low Temp. Phys.; (United States)

DOI:https://doi.org/10.1007/BF00657172· OSTI ID:7324933

Sweedler, A R ^[1]; Cox, D E; Moehlecke, S; Jones, R H; Newkirk, L R; Valencia, F A

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1. Brookhaven National Lab., Upton, NY

The A-15 phase of chemically vapor-deposited Nb/sub 3/Ge has been investigated by annealing techniques in the temperature range 700 to 1450/sup 0/C and by irradiation with high-energy neutrons (E greater than 1 MeV). By x-ray diffraction analysis the samples were found to contain about 55 wt percent of the A-15 phase, 35 wt percent of tetragonal Nb/sub 5/Ge/sub 3/, and minor amounts of NbO/sub 2/, NbO, and hexagonal Nb/sub 5/Ge/sub 3/. The superconducting transition temperature T/sub c/ and lattice parameter a/sub o/ of the A-15 phase have been measured as a function of annealing temperature and neutron irradiation. T/sub c/ for the unirradiated sample remained above 19/sup 0/K for long-term anneals in the temperature range 700 to 1000/sup 0/C but decreased rapidly above 1000/sup 0/C, reaching a limiting value of about 6/sup 0/K at 1250/sup 0/C, compared to the as-deposited value of about 20/sup 0/K. The decrease in T/sub c/ was accompanied by an increase in a/sub o/ and an increase in the amount of tetragonal Nb/sub 5/Ge/sub 3/ to about 50 wt percent. The observed decrease in T/sub c/ was irreversible in that subsequent annealing at 1100/sup 0/C did not result in any increase in T/sub c/ or decrease in a/sub o/. The sample having a T/sub c/ of about 21/sup 0/K was found to exhibit no superconductivity to 1.5/sup 0/K after exposure to a fluence of approximately 5 x 10/sup 19/ n/cm/sup 2/. An increase in a/sub o/ was also found as a function of neutron irradiation. However, in this case the effects were reversible. It is concluded that the stoichiometric composition is metastable and upon annealing transforms to a stable, Nb-rich A-15 phase containing about 83 at. percent Nb with a T/sub c/ of approximately 6/sup 0/K accompanied by precipitation of tetragonal Nb/sub 5/Ge/sub 3/.

• OSTI ID: 7324933
• Journal Information: J. Low Temp. Phys.; (United States), Vol. 24:5/6
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
GERMANIUM ALLOYS
PHYSICAL RADIATION EFFECTS
TRANSITION TEMPERATURE
NIOBIUM ALLOYS
ANNEALING
BINARY ALLOY SYSTEMS
CHEMICAL VAPOR DEPOSITION
FAST NEUTRONS
HIGH TEMPERATURE
INTERMETALLIC COMPOUNDS
MEV RANGE 01-10
SUPERCONDUCTIVITY
X-RAY DIFFRACTION
ALLOY SYSTEMS
ALLOYS
BARYONS
CHEMICAL COATING
COHERENT SCATTERING
DEPOSITION
DIFFRACTION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTARY PARTICLES
ENERGY RANGE
FERMIONS
HADRONS
HEAT TREATMENTS
MEV RANGE
NEUTRONS
NUCLEONS
PHYSICAL PROPERTIES
RADIATION EFFECTS
SCATTERING
SURFACE COATING
THERMODYNAMIC PROPERTIES
360106* - Metals & Alloys- Radiation Effects
656102 - Solid State Physics- Superconductivity- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena- (-1987)