MELT PROCESSING OF YBA2CU3O7-X

Sintering YBa2Cu3O7-x bulk forms at 1050-degrees-C followed by annealing at 980-degrees-C causes the development of a thick oriented surface layer (Lotgering factor = 0.7). The thickness of the layer depends on the thermal treatment, which is a two-step sintering process. Firing at 1050-degrees-C for 2.5 h followed by 30 h at 980-degrees-C leads to the development of a 0.1-mm-thick surface layer, with clear indication that longer annealing would result in a thicker film. Some orientation develops during uniaxial compaction of the powders. Lotgering orientation factor calculation from X-ray diffraction analysis. SEM, and TEM were used to characterize the microstructure of these samples. T(c) was similar to that of conventionally processed high-density samples, between 83 and 87 K. Some thermal treatments resulted in samples that displayed high resistivity above T(c), possibly caused by segregation of Cu to the grain boundaries.