(La_((0.7-x))Y_(0.3))_(2/3)Ca_(1/3)MnO_3的晶体结构研究

Study of crystal structure about(La_((0.7-x))Y_(0.3))_(2/3)Ca_(1/3)MnO_3

利用标准的固相反应法制备了(La0.7Y0.3)2/3Ca1/3MnO3和La空位(La0.62Y0.3)2/3Ca1/3MnO3锰氧化物粉末样品。X射线衍射(XRD)测量分析表明样品均为单相,并且在300K到30K温度范围内结构没有发生改变,单胞仍然具有正交对称性(Pnma)。并用Rietveld全谱拟合法对X射线衍射测量所得的晶体结构衍射谱进行了拟合。结果表明,晶体结构参数(a,b,c)和晶胞体积(v)随温度发生了明显变化,Mn-O键长随温度减小单调增大,而Mn-O-Mn键角呈单调减小,这也说明存在静态的Jahn-Teller效应。

Some power samples of manganese oxides （La（0.7-x）Y0.3）2/3Ca1/3MnO3 and （La（0.7-x）Y0.3）2/3Ca1/3MnO3 with La-vaeaney were prepared with the solid-state reaction method. Both samples are single phase, with orthorhombic symmetry（Pnma）, analyzed by X-ray diffraction instrument, and there is no change in structural symmetry at the temperature range from 300K to 10K. Crystallographic data at room temperature and low temperature are obtained by Rietveld analyses of powder X-ray diffraction data. The result shows the lattice parameters and crystal volume vary distinctly with temperature. The Mn-O bond length increases and Mn-O-Mn bond angle decreases monotonically with temperature decrease, which shows the presence of static Jahn-Teller effect.