Impurity stabilizedA15Nb3Nb - a new superconductor

Abstract

We have succeeded in preparing by chemical vapor deposition essentially single-phase, $A15$ ${\mathrm{Nb}}_3$Nb with the addition of small amounts of Ge or Si. The compositions and lattice parameters of the five samples reported on here are as follows: ${\mathrm{Nb}}_3$(${\mathrm{Nb}}_{0.92}$ ${\mathrm{Ge}}_{0.08}$), 5.239 Å; ${\mathrm{Nb}}_3$(${\mathrm{Nb}}_{0.82}$ ${\mathrm{Ge}}_{0.18}$), 5.230 Å; ${\mathrm{Nb}}_3$(${\mathrm{Nb}}_{0.71}$ ${\mathrm{Ge}}_{0.29}$), 5.219 Å; ${\mathrm{Nb}}_3$(${\mathrm{Nb}}_{0.61}$ ${\mathrm{Si}}_{0.39}$), 5.213 Å; ${\mathrm{Nb}}_3$(${\mathrm{Nb}}_{0.46}$ ${\mathrm{Si}}_{0.54}$), 5.192 Å. Using these compositions and lattice parameters, the lattice parameter for pure $A15$ ${\mathrm{Nb}}_3$Nb is found to be 5.250 ± 0.005 Å. The low-temperature specific heat of all five samples was measured from 1.4 to 11 K, showing bulk superconduting transitions in all cases, with $T_c$ midpoint and $\frac{\Delta C}{\gamma T_c}$ values as follows: ${\mathrm{Nb}}_3$(${\mathrm{Nb}}_{0.92}$ ${\mathrm{Ge}}_{0.08}$), 5.2 K and 1.24; ${\mathrm{Nb}}_3$(${\mathrm{Nb}}_{0.82}$ ${\mathrm{Ge}}_{0.18}$), 4.15 K and 1.16; ${\mathrm{Nb}}_3$(${\mathrm{Nb}}_{0.71}$ ${\mathrm{Ge}}_{0.29}$), 3.6 K and 1.27; ${\mathrm{Nb}}_3$(

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This publication has 13 references indexed in Scilit:

• Properties of high-Tc,A−15Nb3Si: An extrapolation
  Physical Review B, 1979
• Specific heat of bccMo1−xTcx
  Physical Review B, 1979
• Electronic properties ofNb3Ge andNb3Al from self-consistent pseudopotentials. I. Band structure and density of states
  Physical Review B, 1979
• The phase diagram of the niobium-germanium system
  Journal of the Less Common Metals, 1978
• Neutron irradiation of superconducting compounds
  Journal of Nuclear Materials, 1978
• Composition versus a0 and T c relations in superconducting ’’Nb3Ge’’ thin films
  Journal of Applied Physics, 1976
• The Preparation of High T c Nb3Ge Superconductors by Chemical Vapor Deposition
  Journal of the Electrochemical Society, 1976
• High Tc Nb3Ga and Nb3Ge by CVD
  Physics Letters A, 1974
• Heat Capacity Measurements on Small Samples at Low Temperatures
  Review of Scientific Instruments, 1972
• Transition Temperature of Strong-Coupled Superconductors
  Physical Review B, 1968

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