EFFECT OF AG/AG2O ADDITIONS ON THE RESISTIVE BEHAVIOR OF PREFORMED YBA2CU3O7-DELTA COMPACTS IN THE LOW-TEMPERATURE SINTERING REGIME

Contacts between the individual ceramic particles dictate the resistive behavior of bulk, polycrystalline, preformed YBa2Cu3O7-δ compacts in the low temperature sintering regime. Ag/Ag2O additions to performed 123 are investigated, with an aim to lower the sintering temperature required to achieve macroscopic zero resistivity in particulate cermet superconductors. The addition of Ag/Ag2O results in enhanced resistive properties due to improved interparticle contacts. The thermal decomposition of Ag2O in the presence of 123 is unaltered, as shown by DTA and TGA analysis. Hence, the presence of Ag2O at temperatures higher than its normal decomposition temperature appears unlikely. For sintering temperatures below 600°C, internal oxidation due to dissociation of Ag2O may serve as an efficient mechanism for oxygenating the 123 phase. However, for sintering temperatures close to 800°C, Ag additions are as effective as Ag2O additions and the benefit of oxygen donation by Ag2O appears to be small. The addition of Ag/Ag2O and the use of high compaction pressures, reduce the minimum sintering temperature to attain macroscopic zero resistivity from 900-950°C to ∼ 800°C. © 1990.