SOLID-STATE SINTERING OF YBA2CU3OX IN DIFFERENT OXYGEN PARTIAL PRESSURES

The effect of oxygen partial pressure, ranging from 0.001 to 1.0 atm, and temperature, in the range of 930-degrees-955-degrees-C, on the sol id-state sintering kinetics of the superconducting ceramic YBa2Cu3O7-d elta has been studied. Isothermal compaction rates between 930-degrees and 955-degrees-C reached a maximum at some critical PO2 (PO2CRIT), w ith decreasing rates both above and below this oxygen partial pressure . This behavior was not observed for YBa2Cu3O7-delta sintered at 960-d egrees-C, when a liquid phase is present. The activation energy for si ntering above PO2CRIT has been estimated to be approximately 190 kJ/mo l, whereas below PO2CRIT it was found to be approximately 130 kJ/mol. The oxygen ion diffusion was considered to be the rate-determining ste p above PO2CRIT, while it is hypothesized that lattice strain caused b y the formation of oxygen ion vacancies below PO2CRIT affected the rat e of sintering.