Synthesis of Perovskite Oxides by Hydrothermal Processing - From Thermodynamic Modelling to Practical Processing Approaches

The present chapter aims to provide a conscious review of the principles associated with the chemical reactions and the control of the parameters related to the hydrothermal processing of perovskite-structured compounds. Highlights on fundamental principles of the thermodynamic modelling coupled with the relevant technical expertise gained during the past two decades are discussed. Achievements conducted in the early 1990s on thermodynamic modelling of hydrothermal reactions, leading to the estimation of the chemical reaction equilibrium occurring under specific conditions, i.e. above 100°C and 0.1 MPa, are discussed. Additional efforts resulted in different thermodynamic models that predict crystal growth kinetics and the stability for particle nucleation; the models based on chemical population balance approaches are also considered. However, these models do not apply for perovskite compounds containing rare earth elements that crystallize under hydrothermal conditions above 250°C, i.e. orthorhombic lanthanum chromite perovskite. Hence, the final part comprises a literature survey for the experimental research work conducted on various perovskite species produced via hydrothermal treatments, emphasizing the relevant conditions that led to the stoichiometric single-phase crystallization.