Melt Processing of YBa2Cu3O7‐x

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Abstract
Sintering YBa2Cu3O7‐x bulk forms at 1050°C followed by annealing at 980°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°C for 2.5 h followed by 30 h at 980°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 un‐axial 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. Tc 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 Tc, possibly caused by segregation of Cu to the grain boundaries.