Thermodynamic Studies as Predictive Tools of the Behavior of Electroceramics Under Different Hydrothermal Environments

Thermodynamic simulations are performed in all areas of materials processing because of the advances that have taken place in computer software for complex non-ideal calculations, together with the increasing availability of evaluated data for different phases. In the present work, a thermodynamic model of electrolytic solutions was applied to determine the reaction conditions favoring the hydrothermal synthesis of the following electroceramics: zinc ferrites, sodium niobates, and lead zirconates. Stability and yield diagrams were constructed relating the equilibrium concentration of all of the aqueous and solid species as functions of temperature, pressure, pH, and input reagent concentrations. The theoretical predictions avoided the empirical trial-and-error method of synthesis and were corroborated by experiments. The results demonstrate the important role that such thermodynamic simulations can play in significantly reducing the time and costs associated with hydrothermal processing.