MAGNETIC-PROPERTIES OF POLYCRYSTALLINE R1.5CE0.5SR2CU2NBO10 (R=EU, ND, AND SM) HIGH-T(C) SUPERCONDUCTING CERAMICS

Magnetic characterization has been performed on the superconducting me mbers of the R1.5Ce0.5Sr2Cu2NBO10 (R = Eu, Nd, and Sm) series. These m aterials are related to the YBa2Cu3O7-delta structure through the repl acement of the CuO chains with NbO2 planes, and the single rare-earth elements with a R2O2 fluorite structure. Measurements of the lower cri tical-field curve, irreversibility line, volume fraction, Meissner fra ction, and magnetic relaxation are reported for each compound. No evid ence of intergrain weak-link behavior down to 0.1 Oe is observed. Esti mates of the zero-field intragrain critical current density from high- field hysteresis curves taken at 6 K for the Nd-, Sm-, and Eu-based sy stems are 2.7 x 10(4), 3.3 x 10(4), and 4.7 x 10(4) A/cm2, respectivel y.