Microstructure and Critical Current Densities of PbMo₆S₈ in Hot-Worked Mo-Sheathed Wires

Abstract

The critical current densities, Jc, of hot-worked Mo-sheathed PbMo₆S₈ wires are affected very much by their composition and heat treatments. For example, Jc for Pb_1+xMo₆S_7.5 wires heat treated at 700°C took a maximum value at x = 0.02 (Jc = 2.1–2.9 × 10⁸ A/m² at 8 T), and decreased mono-tonically with increasing x (Jc ≈ 0.8 × 10⁸ A/m² for x = 0.05, and 0.3 × 10⁸ A/m² for x = 0.1). We have investigated the Jc values for many Pb_1+xMo₆S_8-y sample wires, and microstructural analyses have been performed using SEM and TEM techniques. It has been demonstrated that Jc is not determined only by the grain size, which is only of order 0.1–0.3 μm at optimum, and that the connections between PbMo₆S₈ grains are in general not complete.