Intelligent Synthesis of Smart Ceramic Materials

Abstract

AbstractThis article is focus on the hydrothermal synthesis of smart ceramic materials that have a perovskite‐type structure. Perovskite compounds have the general formula ABO3, where the A cation is relatively large and of low valence and the B cation is relatively small.Hydrothermal synthesis involves numerous simultaneous reactions between dissolved and solid species in an aqueous system to form anhydrous multicomponent oxides. Hydrothermal media may provide an effective reaction environment for synthesizing numerous smart ceramic materials from a variety of precursor reagents (e.g., water‐soluble salts, hydroxides, oxides) in the form of polycrystalline solids, thin films, and single crystals.In particular, phase‐pure ceramic materials that have controlled stoichiometry and morphology can be hydrothermally synthesized in a single experimental step from simple and inexpensive precursors at moderate temperatures and pressures far below those required for conventional techniques. It is important to select a precursor system that is both reactive and cost‐effective. However, the reactivity of a precursor system can be judged only by optimizing the processing variables such as reagent (precursor) concentrations and ratios, pH, temperature, and pressure, which can be extremely time‐consuming due to the large number of variables involved. To improve the efficiency of evaluating a precursor system, a comprehensive thermodynamic model that simulates hydrothermal reactions has been developed. This model is a part of the OLI software. The simulation approach discussed here has been validated for numerous perovskite‐type multicomponent oxide systems, which include alkaline‐earth titanates and zirconates, lead titanate, various solid solutions of lead zirconate titanate, lead magnesium niobate, and lead zinc niobate. In this article, modeling and experimental validation of selected hydrothermal systems are presented.