Microstructural and magnetisation study in melt-grown YBaCuO samples

The effect of Y2BaCuO5 (211) and silver on the microstructure of melt-grown YBa2Cu3O7-x (123) has been systematically investigated. An optimal amount (28 mol%) of 211 in the starting composition of 123 with 5 wt.% of silver gave critical current densities > 104 A/cm2. Magnetisation 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 used to analyse the magnetisation of the optimised composition (123 + 28 mol% + 5 wt.% Ag). An anticlockwise tilt observed in the magnetisation curve above 70 K in the optimised sample has been explained as being due to the presence of an additional paramagnetic contribution arising from 211 particles present in the 123 matrix. © 1995.