Strong pinning in ternary (Nd–Sm–Gd)Ba2Cu3Oy superconductors

Abstract

We have studied the flux pinning in melt-textured ( Nd 0.33 Sm 0.33 Gd 0.33 ) Ba 2 Cu 3 O y NSG-123 superconductors with various numbers of Gd 2 BaCuO 5 (Gd-211) particles. Transmission electron microscopy(TEM) showed that submicron Gd-211 particles are uniformly distributed in the superconductive matrix. Dark-field TEM observations further showed that a high density of RE rich RE 1+x Ba 2−x Cu 3 O y (RE-123ss) clusters 3–10 nm in size were distributed in the NSG-123 matrix. A strongly developed fishtail was observed in the magnetization hysteresis loops of all the samples. A critical current density of 100 kA/cm2 (77 K) was achieved at the secondary peak field of 2 T for the H∥ c axis in the NSG-123 sample with 10 mol % Gd-211. Large grain NSG-123 pellets with 30 mol % Gd-211 and 20 wt % AgO 2 , 30 mm in diameter and 15 mm in height, exhibited a single-cone profile with a peak value of 1.2 T at 77 K. A higher trapped-field value of 1.5 T was recorded at 2 T, reflecting the secondary peak effect.