LaSr_(2-x)Ca_xV_3O_(9±y)的制备、结构和价态影响

Preparation, Structure and Influence of Valence State on LaSr_2-_xCa_xV_3O_(9±y)

采用新的合成方法制备了一类新的化合物LaSr_(2-x)Ca_xV_3O_(9±y).X射线粉末衍射分析证实它们是单一化合物.利用计算机及自编软件对其进行了指标化并计算了它们的晶胞常数.结构数据表明,随钙含量的增加,LaSr_(2-x)Ca_xV_3O_(9±y)发生了从立方到正交到立方的相转变.热重和光电子能谱表明,新化合物中的钒是以V^(3+)和V^(4+)的低价态形式存在.它们具有较低的电阻率.

New compounds LaSr_(2-x)Ca-xV_3O_(9±y)(x=0.0, 0.67, 1.0, 1.33 and 2.0)have been synthesized with a simple new method X ray powder diffraction results indicate that they are single compound. Their lattioe constants are calculated. The structure of LaSr_(2-x)Ca_xV_3O_(9±y)changed from cubio to orthorhombic and back to cubic with the increase of calcium content. The results of weight gain in TG and XPS curves show that vanadium with lower valent state is oxidized to higher valent state at higher temperature. The oxygen content of new compounds are calculated from the weight gain. It is shown that V^(3+)and V^(4+)may coexist In LaSr_(2-x)Ca_xV_3O_(9±y). These compounds show that low resistivity.