Thermal process effect of lead–indium alloy on crystal structure and superconductivity

Bulk samples of lead (Pb)–indium (In) alloys, Pb100−xInx (x8.23, 4.0 and 2.0 wt.%) were prepared and were annealed at a temperature near the melting temperature every 10 days from 10 to 50 days. The lattice constant of each alloy approaches an equilibrium value with increasing in the annealing time ta and decreases with increasing In concentration. Isothermal magnetization (M)–external magnetic field (H) characteristics in the mixed state have not shown the change from irreversible curve to reversible one, which is one of the evidences for appearance of the vortex liquid. The upper critical field and the superconducting transition temperature Tc increased with increasing In concentration. The correlative change between the superconducting coherence length at 0 K and ta could not be observed.