Characterization Of The B-Site Doped Perovskite Niobate And Ferrite

Perovskite oxides have a wide physical and chemical properties, such as properties of ferromagnetism, ferroelectrieity, piezoelectricity, colossal magnetoresistances, and so on. It has now become a hot topic in the study of condensed solid state physics and a leading subject. Perovskite oxide is an important class of materials, characterized by subtle structural distortions from the cubic aristotype structure. They have very important structural, electrical and magnetic properties. These important materials have received a large amount of academic interests and could be used as oxygen permeation membranes, partial-oxidation catalysts or components of a solid-oxide fuel cell.We discussed the magnetic and photocatalytic of B-site doped niobates and ferrites. The main research works were as follows, a series of potassium barium niobium catalytic materials. K_0.8Ba_0.2Nb O₃, K_0.8Ba_0.2Fe_0.2Nb_0.8O₃ and K_0.8Ba_0.2Mn_0.2Nb_0.8O₃ were synthesized by hydrothemal method. The composition of the niobate depended on the mineralizer KOH, reaction tempertaure and reaction time. The samples were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, infrared spectroscopy, UV-Vis and magnetic properties. Through the analysis of SEM, the compound has uniform particle size, structure and morphology compared with the regular one. XPS test results showed that the synthesized Nb composite materials have mixed valences of Nb⁴⁺ and Nb⁵⁺. The magnetic analysis showed that the sample K_0.8Ba_0.2Nb O₃ is paramagnetic. Magnetic study found that the sample K_0.8Ba_0.2Fe_0.2Nb_0.8O₃ phase transiton point TN=42K, from antiferromagnetic to paramagnetic. The sample K_0.8Ba_0.2Mn_0.2Nb_0.8O₃ phase transiton point TN=55 K, from antiferromagnetic to paramagnetic.Through a mild hydrothermal method, we synthetized the Sm Fe_0.5Mn_0.5O₃, which was a perovskite structure compound. The samples were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, infrared spectroscopy, UV-Vis, magnetic and photocatalytic properties. Through the analysis of SEM, the compound has the uniform particle size, structure and morphology compared with the regular one. XPS test results showed that the Fe and Mn in the Sm Fe_0.5Mn_0.5O₃ appeared with the valence of Fe³⁺and Mn³⁺. The magnetic analysis showed that the sample Sm Fe_0.5Mn_0.5O₃ has weak ferromagnetism. The samples were employed as photodegration catalyst of methylene blue, photocatalytic analysis results showed that the perovskite type structure of the compounds presented with high photocatalytic activity both in the UV and visible light range.