Effects of coprecipitation conditions and processing on powder stoichiometry and properties of oxalate-derived high-Tc YBa2Cu3O7-n ceramics

This paper reports the effects of coprecipitation conditions and processing on the stoichiometry of high Tc oxalate precursor powders investigated. The oxalates of yttrium, copper, and barium were coprecipitated from the reaction between the metal nitrate mixture and (Et3NH)2C2O4. Optimized processing parameters previously determined for this system1 were subsequently used to generate sintered and O2 annealed pellets. Powder stoichiometry was controlled by solution pH, concentration, temperature, and post-coprecipitation surface treatments. XRD and chemical analysis were used to characterize powders, while pellets were characterized by SEM, XRD, SQUID, and density measurements. Results show that solution pH, concentration, and calcination temperature significantly affected powder stoichiometry, whereas precipitation temperature markedly influenced final densification and impurity phase content in the sintered pellets. Powder stoichiometry was also found to be strongly correlated to the phase development microstructure, and high Tc properties exhibited by the sintered pellets