Hydrothermal Synthesis And Characterization Of The Perovskite Chromate

Hydrothermal synthesis is the process which makes the reactants to the products in the sealed the system in certain temperature with the medium: water. Under this condition, the physical and chemical properties of the substances will change. In this process water has two functions: one is to provide the pressure and the other is to provide a uniformly reaction environment, which makes some difficult reaction react in a mild temperature. Owe to the low reaction temperature some products have different structures and properties. In the solid state chemistry, perovskite structure consists of one of the most basic and the most important structure and the complex oxides with the perovskite structure and the related structures have a bright future in application. So many people are interested in the synthesis, structure and properties.In this paper, we systematically investigate the application of the hydrothermal synthesis of the complex oxides with the perovskite and other related structures. To some solid state oxide electrolytes synthesized by other methods such as solid state reaction, co-deposition and sol-gel methods, we try to get these oxides by a more mildly method, such as the hydrothermal method in order to investigate the difference of the structures, compositions and the properties among these synthesis methods. So we can recognize the relationship between the synthesis andthe composition, the structure and the properties of the materials. This isthe most important in thedirectional synthesis of the materials. So we constitute the goal below:1. Complex oxides often are made in 1200℃, whether we coulddecrease the synthesis temperature is meaningful in synthesizing some new compounds and investigate the synthesis mechanism. So we try our best in the system of La(OH)₃-CrCl₄-KOH-H2O.2 .One of the specialty of the hydrothermal synthesis is to prepare the mixed valence and the high valence compounds.So we do a lot of work to get themixed valence compounds.Through our work we get some results as below:1. LaCrO₃ has been directly prepared by a mild hydrothermal method in the system KOH-K₂Cr₂O7-CrC13-La(OH)₃-H2O. The influence of nominal materials, KOH concentration and the crystalline temperature on the formation of pure phase products were investigated.2. Mixed valence compound, La0.87Sr0.13CrO3 has been directly prepared by a mild hydrothermal method in the system La(OH)3-KOH-K₂Cr₂O7-CrCl₃-Sr(NO₃)₂-H₂O.AndMixed valence compound, LaCrMnO₃ and LaCrFeO₃ has been directly prepared by a mild hydrothermal method in the system KOH-K₂Cr₂O7-CrCl3-MnCl₂-H2O andKOH-K₂Cr₂O7-CrCl3-Fe(NO₃)₂-H2O.