Critical current density and irreversibility line in melt-textured YBCO with CeO2 addition

We prepared melt-textured YBCO with CeO2 addition in order to enhance flux pinning. SEM photographs showed that Y2BaCuO5 precipitates of about 1 mu m size were uniformly distributed in YBCO grains. Magnetization hysteresis at various temperatures was measured to investigate critical current density using a SQUID magnetometer. Critical current density at 77 K in a field of 1 T was about 2 x 10(4) A/cm(2) and increased by lowering temperature. The irreversibility line determined from the closing points of the magnetization hysteresis was shifted to high fields. The temperature dependence of the irreversibility field followed a power law, H-irr proportional to (1-T/T-c)(n) with n approximate to 1.4.