Study on superstructure in ion co-doped BiFeO3 by using transmission electron microscopy

La3+and V5+co-doped Bi Fe O3 ceramics are synthesized by rapid liquid sintering technique. The modulated structure in Bi0.85La0.15Fe0.97V0.03O3 is investigated by using transmission electron microscopy(TEM). Two kinds of superstructures are observed in the samples. One is the component modulated superstructure and twin-domain, which is generated by La3+ordered substitution for Bi3+and frequently appears. The chemical composition of the superstructure is explored by x-ray energy dispersive spectroscopy(EDS). The model of the ordered structure is proposed. Simulation based on the model is conducted. The second is the fluorite-type δ-Bi2O3 related superstructure. The relation between the ferroelectric property and the microstructure of the sample is also discussed.     

二十面体AlPdMn准晶近似相的电子结构研究

基于二十面体AlPdMn准晶近似相的Quandt-Elser结构模型,使用VASP第一性原理计算程序包,计算了二十面体AlPdMn准晶近似相的电子态密度NE和电荷密度.计算结果表明,i-AlPdMn准晶近似相的DOS曲线上,在Fermi能EF附近形成了一个宽度约为1 eV的很深的赝能隙;Mn的d峰被宽化,并出现在能量较低的位置上;价电子被局域在Al—Mn,Al—Pd,Al—Al,Mn—Pd之间的中间区域,具有共价键的特征,且Al—Mn间的共价键最强.赝能隙的形成和化合键的共价键特征可以很好地解释i-AlPdMn准晶和准晶近似相的特殊物理性质.