Properties of high-T/sub c/, A-15 Nb/sub 3/Si: An extrapolation

Journal Article · Wed Oct 31 23:00:00 EST 1979 · Phys. Rev., B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.20.3647· OSTI ID:5848671

Stewart, G R; Newkirk, L R; Valencia, F A

We have measured the low-temperature specific heats of two samples of A-15 Nb-Si prepared by chemical vapor deposition. From the specific-heat data, low-T/sub c/, A-15 Nb-Si is found to have a ..gamma.. of 15.2 +- 1.5 mJ/mole K/sup 2/ and a Debye temperature, THETA/sub D/, of 319 +- 10 K, for a mole containing four atoms. In addition, the low-temperature specific heat of arc melted Nb/sub 0.82/Ge/sub 0.18/(A-15 structure) has been measured. The ..gamma.. was found to be 15.2 +- 1.0 mJ/mole K/sup 2/ and THETA/sub D/ was 345 +- 10 K. Using these data, the properties of stoichiometric (high-T/sub c/) Nb/sub 3/Si are extrapolated from the substoichiometric Nb-Si samples measured, by analogy to the Nb-Ge system. Stoichiometric, single-phase A-15 Nb/sub 3/Si, if preparable, should have a ..gamma.. of 30 mJ/mole K/sup 2/ and a THETA/sub D/ of 275 K. By calculating lambda, the electron-phonon coupling constant, and treating T/sub c/ as a variable (15--30 K), the electronic density of states, N (0), is extracted from this extrapolated ..gamma.. and is found to be low, varying from 1.38 states /(eV atom) at T/sub c/=15 K to 0.91 states /(eV atom) at T/sub c/=30 K. The N (0) calculated for the low-T/sub c/ Nb/sub 0.82/Ge/sub 0.18/ is 1.01 states/(eV atom) and is remarkably close to the 1.08 states/(eV atom) calculated for the high-T/sub c/ Nb/sub 3/Ge.

• Research Organization: University of California, Los Alamos Scientific Laboratory, Los Alamos, New Mexico 87545
• OSTI ID: 5848671
• Journal Information: Phys. Rev., B: Condens. Matter; (United States), Journal Name: Phys. Rev., B: Condens. Matter; (United States) Vol. 20:9; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
ALLOYS
DEBYE TEMPERATURE
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTRON-PHONON COUPLING
ENERGY-LEVEL DENSITY
GERMANIUM ALLOYS
NIOBIUM ALLOYS
NIOBIUM COMPOUNDS
NIOBIUM SILICIDES
PHYSICAL PROPERTIES
SILICIDES
SILICON COMPOUNDS
SPECIFIC HEAT
SUPERCONDUCTIVITY
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS