Densification and microstructural studies on Y-Ba-Cu-O superconducting oxide

Abstract

The effects of sintering conditions of cold-pressed superconducting YBa₂Cu₃O_x pellets made from calcined powders using different raw materials are reported. Very slow densification has been noticed between 800 and 920 degrees C with the powder of 1.7 mu m size. In general at any sintering temperature the rate of densification in the first three to four hours of sintering is found to be very high and thereafter it is slower. Pellets sintered at 960 degrees C contain other non-superconducting phases besides the superconducting 123 phase, due to the decomposition of the latter. Abnormal discontinuous grain growth and faceted grains are observed in the samples sintered for longer periods. It is further noticed that the low-temperature oxidation at 450 degrees C is found to cause intergranular and transgranular cracks.