ANALYSIS OF THE SPATIAL-DISTRIBUTION OF Y2BACUO5 INCLUSIONS IN LARGE-GRAIN YBA2CU3O7-DELTA

High values of critical current density, J(c), in large-grain supercon ducting melt-processed YBa2Cu3O7-delta (YBCO, Y-123) have been reporte d to correlate closely with the distribution of Y2BaCuO5 (Y-211) parti cles in the Y-123 phase matrix. Extensive image analysis of the homoge neity of the Y-211 particle distribution in a large-grain sample has b een performed on high-resolution, secondary scanning electron microgra phs of seeded melt-processed YBCO. The variation of key parameters, su ch as area fraction, number density and size along the a/b axis of the Y-123 grain has been investigated in detail as a function of distance from the centre of the seed. Both area fraction and number density of Y-211 particles are observed to increase continuously with distance, whereas the mean and standard deviation of the size distribution decre ase slightly towards the grain boundary. This suggests that the increa se in area fraction can be attributed to an increase in number density of the Y-211 particle distribution along the a/b axis of the specimen . The implications for Y-211 particle pushing, ripening and coalescenc e are discussed in the light of these results. (C) 1998 Chapman & Hall .