Hydrothermal Synthesis And Characterization Of The Perovskite Manganites

The conventional syntheses for multicomponent perovskite manganites are through high temperature solid state reactions between oxides and/or carbonate precursors. Repeated cycles of milling and calcinations are carried out to achieve the completion of solid state reactions. Relatively high temperatures, typically above 1200℃are required because of the limited diffusion during calcinations. The advantages of solid state reaction are the ready availability of oxide precursors and the low cost for powder production. However, its disadvantages are clear. High temperature calcinations in some cases may lead to the decomposition of products of the formation of undesirable phases. Particle size reduction by milling can introduce chemical impurities into the ceramic product, which may severely influence the final properties of perovskite manganites. Hydrothermal method, involving heating metal salts, oxides or hydroxides as a solution or suspension in a liquid elevated temperature and pressure, offers an alternative synthesis route for the multicomponent ceramic oxides. Because the reactions are carried out in solution, the physicochemical properties of many reactions will change. Compared to high temperature solid state reactions, hydrothermal reactions need relatively low temperatures which favors the formation of low agglomeration, homogeneity and good sinterability ceramic powder. In addition, hydrothermal method is an open route to metastable phases. In this study, we focus on the hydrothermal synthesis of perovskite manganites. In the system that has been prepared by traditional methods, a more soft synthesis route is explored and...