A COMPARISON OF THE EFFECTS OF PTO2 AND BASNO3 ADDITIONS ON THE REFINEMENT OF Y2BACUO5 AND MAGNETIZATION OF TEXTURED YBA2CU3O6+X

Y2BaCuO5, (211) and liquid (L = 3 BaCuO2: 2CuO) were used as the precu rsor materials to study the effect of additions of BaSnO3, and PtO2, o n the coarsening behaviour of 211 particles in the liquid above the pe ritectic temperature of YBa2Cu3O6+x (123), and the magnetic properties after melt texturing. Additions of BaSnO3 and PtO2 both reduced the c oarsening of 211, but PtO2 did so much more effectively. The PtO2 addi tions were found to refine 211 by altering the 211/liquid interfacial energy and/or Y diffusivity, and not by acting as heterogeneous nuclea tion sites. BaSnO3 additions were found to not be inert in the melt. T hey reduce 211 coarsening by acting as a Y sink. Magnetization measure ments at 20, 40 and 60 K on crushed melt-textured 123 samples showed e nhanced intragrain flux pinning effects in samples prepared from 211 L + PtO2 as compared with 211 + L + BaSnO3 or 211 + L precursor sampl es.