Phase Evolution in Ag:(Bi,Pb)2Sr2Ca2Cu3Ox Composite Powder

Abstract

The phase evolution in submicron superconducting composite particles prepared by spray pyrolysis was followed from the droplet-particle formation stage through the powder calcination stage. Aerosol was generated ultrasonically (1.7 MHz) from a urea-modified nitrate precursor solution containing 20 wt% silver. The salt decomposition process was aided by self-combustion of the droplets due to the presence of the urea. A uniform distribution of all of the constitutive chemical elements of the (Bi,Pb)-2223 phase was confirmed by energy dispersive spectroscopy. Ag is present together with (Bi,Pb)-2212, 2201, and (Sr,Ca)i4Cu2404i in submicron equiaxial particles that are aggregates of primary nanoparticles. Initial thermal treatment of these particles increases the 2212 phase content, and forms Ca2Pb04.