Ag Doping Effect on the Superconductivity of Nb3Al Prepared Using High-Energy Ball Milling Method

Ag-doped Nb
₃
Al samples, Nb
₃
(Al
_1.05-x
Ag
_x
), with x = 0, 0.05, 0.1, 0.15, and 0.2 are synthesized using high-energy ball milling method. At first, the raw materials are found to form Nb(Al, Ag)
_ss
solid solution after 3 h of high-energy ball milling. With subsequent heat treatment, sintered at 900 °C for 5 h, a transformation from Nb(Al, Ag)
_ss
into A15 Nb
₃
Al phase occurred. The σ-phase Nb
₂
Al diffraction peaks have been observed in the XRD patterns of pure Nb
₃
Al. However, with Ag doping, no σ-phase Nb
₂
Al has been detected. SEM images show an obvious difference, where the crystalline grain can be clearly observed in the matrix Nb
₃
Al phase, but the grain boundary was blurred in the doped samples. The M-T curve illustrated that the superconducting transition temperature of the Ag doped Nb
₃
Al compounds decreased with increasing dopants, but slight Ag doping can be effective to stabilize the Nb
₃
Al A15 lattice.