Thermodynamic optimization of the PbO-ZrO2-TiO2 (PZT) system and its application to the processing of composites of PZT ceramics and copper

The aim of this thesis was to obtain a consistent set of thermodynamic data for the Cu-Pb-Zr-Ti-O system, by means of the CALPHAD method, and then to calculate phase equilibria and chemical potential diagrams. The thermodynamic properties were described using the compound energy formalism (CEF) as well as the substitutional solution model for various solid phases and the associate model for the liquid phase, while the Redlich-Kister series were used to account for the interactions between species. Associate solution model adopted for the description of the liquid phase in the multicomponent Cu-Pb-Zr-Ti-O system was found to be superior for calculating the relevant phase equilibria in comparison with the twosublattice ionic model, although both models can be successfully applied to the binary systems (Zr-O, Ti-O, Cu-O, Pb-O). The ternary compound Cu2PbO2 was modelled as a stoichiometric compound. Its thermodynamic properties were estimated by experiments. In the modelling of the ternary Cu-Ti-O system the three ternary compounds, Cu3Ti3O, Cu2Ti4O and Cu3TiO4 were taken as stoichiometric compounds. PbTiO3 (tetragonal and cubic forms) and PbZrO3 (cubic form) were considered as stoichiometric compounds in the PbO-TiO2 and PbO-ZrO2 systems, while the tetragonal and orthorhombic PbO solid solutions were described by a substitutional model. The perovskite solid solution series, PbZrxTi1-xO3 was modelled as high temperature cubic form using the substitutional model. Calculated phase diagrams, i.e., predicted phase relations in the multicomponent Cu-Pb-Zr-Ti-O system (isobaric-isothermal sections and chemical potential diagrams) were checked experimentally. (orig.)