Preparation and properties of spray dried precursor powder for melt-processed bulk YBCO ceramics

YBa2Cu3O7-delta precursor powder suitable for the fabrication of melt-processed ceramic has been prepared by spray drying and subsequent calcination. The dehydration and decomposition processes in the nitrate-based spray-dried powder and the formation processes of the YBa2Cu3O7-delta and Y2BaCuO5 phases have been studied in detail using thermal analysis and powder x-ray diffractometry. The morphology, microstructure, and size distribution of the particles in the calcined powder have been investigated using high resolution scanning electron microscopy and particle size analysis and found to contain a significant proportion of submicron sized particles of Y2BaCuO5. Melt-processed samples prepared using the spray-dried powder have been observed to exhibit a significantly finer distribution of the 211 phase than is typically obtained in similar specimens prepared via a mixed oxide route. This provides direct evidence of the suitability of spray-dried precursor powder for the fabrication of large grain, high J(c) melt-processed YBCO ceramics.