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1992
Journal Article
Titel
Crystallization behaviour of freeze-dried YBa2 Cu3 O7-sigma powders at low temperatures
Abstract
Sperconducting YBCO powders were produced via a freeze-drying process using the dissolved acetates as precursors. The 'soft' withdrawal of the solvent in the freeze-drying process in contrast to traditional ceramic techniques gives rise to very fine homogeneous powders consisting of agglomerates with diameters smaller than 300 nm. Due to the short diffusion lengths crystallization temperatures down to 720 xC in air can be realized. The crystallization behaviour depending on temperature and time was investigated with a high temperature powder x-ray diffractometer. The crystallization mechanism was determined to be 2.85 dimensional at a crystallization energy of 374 kJ mol exp-1. Textured thick films (thickness 10-100 micrometres) were prepared on various substates like MgO, YSZ or Ag at annealing temperature above 925 xC.