Valuable mechanistic information, about the reaction pathway in the
formation of the 2223 phase, has been obtained by the use of a solution
synthesis route. The presence of lead in the starting mixture has remarkable
effects on the nature and stability of the different intermediates: i) the
grain size and morphology of Bi2CuO4 is severely
changed, ii) calcium carbonate is partially decomposed to yield the calcium
plumbate, iii) the 2201 phase results stabilized against the formation of
the collapsed phase
Bi17Sr16Cu7O49-δ, iv) the
melting point of the intermediate 2212 is lowered by about 10 °C. All these
effects, due to lead substitution, contribute to promote the formation of
the 2223 phase, controlling also the morphology and properties of the final
product.