Thermochemical investigation of Bi-2223 superconductor doped by PbO

Dissolution enthalpies of Bi2O3, PbO, SrCO3, CaCO3, CuO and Bi1.7Pb0.3Ca2Sr2Cu3O10 at 323.15 K in 6 M HCl were measured by solution calorimetry. On the basis of these data, the enthalpies of the following reactions were obtained: (1) 0.85Bi2O3 (s) + 0.3PbO (s) + 2CaCO3 (s) + 2SrCO3 (s) + 3CuO (s) + 0.075 O2 (g) = Bi1.7Pb0.3Ca2Sr2Cu3O10 (s) + 4CO2; (2) 0.85 Bi2O3(s) + 0.3PbO (s) + 2CaO (s) + 2SrO (s) + 3CuO (s) + 0.075 O2 (g) = Bi1.7Pb0.3Ca2Sr2Cu3O10 (s). It was established that Bi1.7Pb0.3Ca2Sr2Cu3O10 was thermodynamically unstable with respect to the interaction with CO2 and thermodynamically stable with respect to decomposition to the mixture of binary oxides. The standard formation enthalpy of Bi1.7Pb0.3Ca2Sr2Cu3O10 was calculated as following: ΔfH° (Bi1.7Pb0.3Ca2Sr2Cu3O10, 298.15 K) = −3643.3 ± 8.7 kJ mol−1.