MICROSTRUCTURAL AND MAGNETIZATION STUDY IN MELT-GROWN Y-BA-CU-O SAMPLES

The effect of Y2BaCuO5 (211) and silver on the microstructure of melt- grown YBa2Cu3O7-x, (123) has been systematically investigated. An opti mal amount (28 mol%) of 211 in the starting composition of 123 with 5 wt.% of silver gave critical current densities > 10(4) A/cm(2). Magnet isation measurements using a SQUID magnetometer have been utilised to characterise the superconducting properties of the material at various stages of optimisation. Bean's and Kim's critical-state models are us ed to analyse the magnetisation of the optimised composition (123 + 28 mol% + 5 wt.% Ag). An anticlockwise tilt observed in the magnetisatio n curve above 70 K in the optimised sample has been explained as being due to the presence of an additional paramagnetic contribution arisin g from 211 particles present in the 123 matrix.