Effects of second phase and platinum additions on the microstructure and the critical current density of OCMG processed (Nd, Eu, Gd)–Ba–Cu–O

Abstract

Abstract We have investigated the effects of second phase (Nd, Eu, Gd) 2 BaCuO 5 (NEG211) and platinum addition on the superconducting properties for (Nd, Eu, Gd)Ba 2 Cu 3 O Y (NEG123) composite prepared by the oxygen–controlled melt–growth (OCMG) process. The addition of NEG211 slightly decreased the critical temperature ( T c ) and increased the critical current density ( J c ), particularly in a low field region. The secondary peak effect, which is commonly observed in OCMG processed Nd123, was reduced with the NEG211 addition of >10%. Refinement of the NEG211 second phase was achieved by Pt addition, which led to a dramatic increase in both J c values and the irreversibility field. Low field J c varied as V f / d , where V f is the volume fraction and d is the mean diameter of NEG211, supporting the idea that the 211/123 matrix is responsible for the pinning-like melt–processed Y–Ba–Cu–O. However, in a high field region, due to the presence of additional pinning by field–induced pinning centers, such a relationship is not observed. Our results suggests that fine distribution of the second phase is effective in improving pinning properties in the (Nd, Eu, Gd)–Ba–Cu–O composite.