Hydrothermal Synthesis And Characterization Of The Perovskites Ferrite And Manganites

Perovskite oxides have been extensively investigated due to their particular electrical and magnetic property. These most important property make them become the possible candidates as electrolytes used in solid-oxide fuel cells, high-temperature oxygen sensor and catalysts. In the mid-80s the high temperature superconductor's appearance and to the great magnetoresistance's research, causes the perovskite rare earth compound to become the research especially in the 90s the hot spot.The coexistence of ferroelectricity and magnetic order has been observed more recently in the perovskite bismuth oxides with a non-symmetric structure, such as BiFeO₃ and BiMnO₃; hence, they have attracted considerable attention. The phenomenon of simultaneous ferroelectric and magnetic order, that is, particular behavior, presents not only opportunities to study fundamental physics but also potential applications in information storage, communication, and sensors.It is well known that the microstructure of the material plays an important role in its physical properties. The synthesis technique and process are crucial to the microstructure. The size and morphology of BiFeO₃ dependencies of optical, catalytic, magnetic, and transport behaviors have been extensively studied. For the perovskite bismuth oxides, the conventional solid-state reaction at a high sintering temperature is commonly used. Therefore, it is difficult to obtain a single phase, because the volatilization of some reactants leads to an incomplete reaction Although many synthetic routes have been employed, a soft-chemical route to obtain bismuth ferrites with high purity and perfect crystallization. is worth exploring. In this paper ,we synthesized the BiFeO₃ pure powder in the present paper using the hydrothermal method.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. With the basis of large experiments, we investigated the characterization of this materials such nanocrystalline, colossal magnetoresistance and superconductor.In this paper we through fumble suitable condition, using hydrothermal method synthesis the ferroelectricity and the ferromagnetic order BiFeO₃,La_0.6Ba_0.34K_0.06MnO₃ and La_0.46Ba_0.45K_0.09MnO₃. The product composition,structure,appearance,magnetism,thermostble and so on have been characterized in the preliminary survey, provides the help for the material synthesis and the design.In the mild condition, BiFeO₃ was obtained by hydrothermal synthesis. Obtained the pure ferrous acid bismith through the control response condition.The influences of various hydrothermal conditions such as reaction time and temperature on the formation, morphology and crystalline size of products were investigated. And analyzed carefully sought the best synthesis condition under other condition by-product.La_0.6Ba_0.34K_0.06MnO₃ and La_0.46Ba_0.45K_0.09MnO₃ have been prepared in the system of KOH-KMnO₄-MnCl₂-La(NO₃)₃-Ba (NO₃)₂-H₂O. The influence of nominal materials, KOH conce- ntration and the crystalline temperature on the formation of pure phase products were investigated. In the system of KOH-KMnO₄- MnCl₂-La(NO₃)₃-Ba(NO₃)₂-H₂O, We considered that redox or disproportionation reaction may happen. The reaction mechanism of it has been not clearly by now, so the further study needs to be done in the hydrothermal synthesis.