Effects of stoichiometry and neutron irradiation in superconducting A-15 compounds

Technical Report · Sun Jan 01 04:00:00 EST 1978

DOI:https://doi.org/10.2172/6313197· OSTI ID:6313197

Moehlecke, S

The A-15 (A/sub 3/B) compounds comprise an important class of superconducting compounds. In order to gain a clearer understanding of the parameters influencing the superconductivity in these materials, several A-15 compounds have been prepared and the effects of varying stoichiometry, heat treatment, and irradiation with high energy neutrons (E > 1 MeV) on the superconducting transition temperature T/sub c/, Bragg--William order parameter S, and the lattice parameter a/sub 0/, have been studied. The systems investigated include Nb/sub 3/Ge, Nb/sub 3/Al, Nb/sub 3/Pt, Nb/sub 3/Ir, V/sub 3/Ga, V/sub 3/Si and Mo/sub 3/Os. Some of the results may be summarized as follows: 1) for Nb/sub 3/Al, Nb/sub 3/Pt and V/sub 3/Ga, T/sub c/ is a strong function of composition, reaching a maximum value at the ideal stoichiometric composition of 3A: 1B, if that composition exists in the equilibrium phase diagram, 2) irradiation with high energy neutrons at temperatures of approx.150/sup 0/C results in drastic lowering of T/sub c/ for Nb/sub 3/Al, Nb/sub 3/Pt and Nb/sub 3/Ge, but not for Mo/sub 3/Os, 3) T/sub c/ can be recovered by annealing, the recovery temperature being in the range 300-800/sup 0/C depends on the particular compound, 4) the order parameter S, decreases with increasing neutron fluence (decreasing T/sub c/), and is also recoverable upon annealing at the appropriate temperature, 5) the lattice parameter a/sub 0/, increases with increasing neutron fluence, and isalso restored to its original value by annealing. A simple hard sphere model is developed to calculate the dependence of a/sub 0/ on composition within the A-15 phase. Excellent agreement is obtained for the measured values in the Nb--Al, Nb--Pt and V--Ga systems. The results of both compositionally and irradiation induced disorder can be understood on the basis of site-exchange taking placee between the A and B sites in the A-15 structure.

• Research Organization: Universidade Estadual de Campinas (Brazil); Brookhaven National Lab., Upton, NY (USA)
• DOE Contract Number: EY-76-C-02-0016
• OSTI ID: 6313197
• Report Number(s): BNL-25940
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104 -- Metals & Alloys-- Physical Properties
360106 -- Metals & Alloys-- Radiation Effects
656102* -- Solid State Physics-- Superconductivity-- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena-- (-1987)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALLOYS
ALUMINIUM ALLOYS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
GALLIUM ALLOYS
GERMANIUM ALLOYS
HEAT TREATMENTS
INTERMETALLIC COMPOUNDS
IRIDIUM ALLOYS
LATTICE PARAMETERS
MOLYBDENUM ALLOYS
NIOBIUM ALLOYS
OSMIUM ALLOYS
PHASE STUDIES
PHYSICAL PROPERTIES
PHYSICAL RADIATION EFFECTS
PLATINUM ALLOYS
PLATINUM METAL ALLOYS
RADIATION EFFECTS
SILICON ALLOYS
STOICHIOMETRY
SUPERCONDUCTIVITY
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
VANADIUM ALLOYS