Physical and chemical effects of silver additions to ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{CaCu}}_2$${\mathrm{O}}_8$ and (Bi,Pb${)}_2$${\mathrm{Sr}}_2$${\mathrm{Ca}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{10}$

Silver in the form of silver peroxide has been added prior to the sintering step in the preparation of ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CaCu}}_2$ ${\mathrm{O}}_8$ and (Bi,Pb${)}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{Ca}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{10}$. X-ray-diffraction analysis and microscopic examination show no evidence for chemical reaction between the silver and the ceramic superconductors. However, the presence of the silver can affect the phase purity of the final product—the amount of the three-layered high-${\mathit{T}}_{\mathit{c}}$ (110-K) phase can either be increased or decreased depending on the sintering conditions and the starting composition. No evidence can be seen in the x-ray spectra to indicate that the silver is going into either phase. The only effect of the silver is on the thermodynamics and kinetics of the sintering process.