Synthesis、structure And Properties Of New Hexagonal Perovskite-related Oxides

In this thesis, we prepared some new hexagonal perovskite oxides with high temperature solid state reaction. The hexagonal perovskite oxides were characterized by X-ray diffraction (XRD), Energy dispersive spectrometer (EDS), Ac impedance spectroscopy measurement, Magnetism measurement and so on. The reseach work can be composed of three parts:The first part,12R-type Ba4tYMn3O11.5ceramic was prepared via high temperature solid state reaction, and the structure unchanged then fired the12R-type Ba4YMn3O11.5ceramic at800℃in different atoosphere, but increase the temperature to1450℃, the12-layer hexagonal perovskite Ba4YMn3O11.5transformed to6-layer mixed valent Mn+3/+4hexagonal perovskite Ba4YMn3O10.7via a partial-reduction in N2atmosphere. Ac impedance spectroscopy measurement suggested that the6H phase is insulating with a bulk electrical resistivity～107Ωcm at30℃, significantly higher than that for the12R-type Ba4YMn3O11.5by～4orders of magnitude. In addition, the dielectric properties of6H-Ba4YMn3O10.7also reduce, which the dielectric constant εr～17.The second part, Ba4GdMnO11.5-δ ceramics were perpared via high temperature solid state reaction, and we refinement the structures via X-ray diffraction datas. Compared with Ba4YMn3O11.5-δ, when we use similar atomic radius of rare earth elements Gd replace Y, also can have a similar conclusion, which12-layer hexagonal perovskite Ba4GdMn3011.5-5transformed to6-layer structure, and the change of electric propertise obviously. Based on Gd3+have4f7and Mn3+/Mn4+have3d4/3d3electronic configuration, we measured the magnetic data of Ba4GdMnO11.5-δ and discussed the possible interaction between the magnetic ion d-d and f-d electronic.The third part, synthetized Ba6M2M’2M"2017(M=Ca、Na、M’=Nb、Ta、V、P; M"=Ti、V、P、Mn) hexagonal perovskite oxides with high temperature solid state reaction.The main phase of Ba6M2M′M″2O17oxides have been refined. Based on these target compounds, this paper summarizes the sizes and valences of B ion influence on the structure stability of hexagonal perovskite and cubic perovskite, and the synthesis of pure phases were characterized by dielectric properties, conductive properties and magnetism. At Present, we have synthesized the pure phase of Ba6Na2Nb2Mn2O17and Ba6Na2Nb2Mn2O17, which it’s a six layers of cubic perovskite structure. Ba6Ca2Nb2Ti2O17is a12layers of hexagonal perovskite structure, but there always are two cubic phase with the hexagonal phase.When change the relative content of A and B atoms, there is a blance relationshio between the cubic phase and hexagonal phase.