A new process yielding fine Y211 particles in melt-textured Y-Ba-Cu-0 was developed by combining attrition milling of Y123-YZll powder and CeOz addition prior to the partial melting. Beneficial points of the attrition milling are as follows: (1) it allows uniform distribution of the Y211 refiner (CeO,) in the Y123-YZ11 powder mixture, (2) it produces nanocrystaliine Y123 powder with large surface area per unit volume which increases the possibility of Y211 nucleation during incongruent melting and (3) it controls the number and the size of Y211 particles preformed at the calcinationlsintering stage from the off-stoichiometric powder of Y1.8 composition. The Y211 particles of the melt-textured Y123 sample which was prepared from the attrition-milled powder were of submicrometre scale and their distribution was quite uniform. The critical current density (Jc) at 77 K of the melt-textured Y1.8 sample containing fine Y211 (less than 1 pm) was 2.0 x 1 0 ' A cm-* and 1.16 x lo4 A twice the Jc of 1.1 x lo4 A cnr2 (at 1 T) and 0.56 x lo4 A cm+ (at 2 T) of the Y1.8 sample containing coarse Y211 (-5 p m in average size). at 1 T and 2 T, respectively, which is

Sm 2 BaCuO 5 (Sm211) refinement was achieved in Sm-Ba-Cu-O systems melt-textured at various oxygen partial pressures (P O 2 of 0.001-1 atm) via 1 wt% CeO 2 addition and size control of a precursor powder (a mixture of SmBa 2 Cu 3 O 7−y (Sm123) plus Sm211 powder) by means of attrition milling. The resulting Sm211 of the Sm 1.8 Ba 2.4 Cu 3.4 O 7−y (Sm1.8) sample melt-textured without CeO 2 addition was as large as a few tens of µm while the Sm211 of the Sm1.8 sample melt-textured from the attrition-milled powder with 1 wt% CeO 2 addition was as small as 1-2 µm, with uniform Sm211 distribution. The Sm211 refinement achieved is ascribable to both the controlled Sm211 nucleation during incongruent melting and the growth inhibition of the Sm211 in the partial melting state. Furthermore, the Sm211 shape was changed from equiaxed granular in the undoped sample to anisotropic in the samples containing CeO 2 . Effects of oxygen partial pressure on the Sm211 size and the shape was not significant in either the undoped Sm1.8 sample and the CeO 2 -added Sm1.8 sample.