Enthalpy of Formation of Cu2PbO2 and Revision of the Cu2O-PbO Phase Diagram
The stoichiometric compound Cu2PbO2 has been synthesized by solid-state reaction from Cu2O and PbO in a sealed quartz ampoule. The optimum synthesis conditions are 910 K and 260 h. The enthalpy of formation of Cu2PbO2 has been measured with the use of high-temperature calorimeter. The enthalpy of reaction Cu2O + PbO = Cu2PbO2 is – 25.4 ± 1 kJ·mol-1 at temperature 968 ± 5 K. Standard enthalpy and Gibbs energy of formation of the Cu2PbO2 compound from elements and its entropy at 298.15 K are DfH° = – 413.086 kJ·mol-1, DfG° = – 353.165 kJ·mol-1 and S° = 135.165 J·mol-1·K-1. The eutectic reaction L → Cu2O + PbO was found to occur at 1017 ± 5 K. Using the thermodynamic database for Cu-Pb-O system the revised Cu2O-PbO phase diagram is proposed.
Dragan P. Uskokovic, Slobodan K. Milonjic, Djan I. Rakovic
M. Čančarević et al., "Enthalpy of Formation of Cu2PbO2 and Revision of the Cu2O-PbO Phase Diagram", Materials Science Forum, Vol. 494, pp. 67-72, 2005