The formation of Pb-doped 80 K phase from nitrate precursors was studied in the Bi1.84Pb0.34Sr1.91Ca2.00Cu3.04O10.05 system. Sr(Pb, Bi)O3, Ca5Bi14O26, CuO, and CaO were found to be the intermediate compounds reacting to produce 80 K phase between 600 and 820 °C. Synthesis was complete at 800 °C for 24 h. 110 K phase formed at the expense of 80 K phase at temperatures above 820 °C. Partial melting was detected and 80 K and 110 K phases were unstable in the presence of liquid phase. They decomposed to 2201, Cu2O, and (Ca, Sr, Cu) complex oxides. The melting and decomposition were accompanied by oxygen loss.