Yang Ji-Lian

Neutron diffraction study on site occupation of substitutional elements at sub lattices in Fe3 Al intermetallics

Abstract The site occupation of substitutional elements Cr, Mo, Ti, Mn, Ni and Si at sublattices in DO3-type stoichiometric Fe3Al intermetallics, effect of the elements on magnetic moment of the unit cell, and tensile properties at room temperature have been determined my means of neutron diffractometry and mechanical measurement in vacuum. The experimental results indicate that Cr, Mo, and Ti atoms all occupy the next nearest neighbors of Al atoms, Ni and Mn atoms the nearest neighbors, while Si atoms occupy the positions of Al atoms. All the alloying elements investigated in the present work modify the magnetic moment of the two types of Fe atoms in the unit cell. Based on the above results and corresponding mechanical measurements, the effects of the substitutional alloying elements on the intrinsic tensile properties are discussed.

NEUTRON DIFFRACTION STUDY ON (Bi−Pb)2Sr2Ca2Cu3O10

The polycrystalline sample of (Bi–Pb)2Sr2Ca2Cu3O10 with Tc=107 K was prepared. The X-ray diffraction proved that the sample is single phase. The crystal structure study on the sample has been carried out by neutron diffraction. The result shows that its structure is tetragonal body-centre structure with space group of I4/mmm, containing a few oxygen atoms at 4e site in Bi–Pb layers.

Neutron Scattering Study of Sr Substitution for Ba in YBa2Cu3O7-y

Neutron diffraction and inelastic scattering were carried out on YBa2-xSrxCu3O7-y (x=0.5, 1.0, 1.25). It was confirmed that the substitution of Sr for Ba in YBa2Cu3O7-y increases the oxygen vacancies in the Cu O chain. Moreover, the substitution strengthens the coupling between the Ba O plane and the Cu O chain, and reduces the crystal stability. These are the possible causes of Tc depression for Sr substituted YBa2Cu3O7-y.

Structure Refinement of Bi2Sr1.855Ca1.145Cu2O8 from Neutron Data

Neutron diffraction study on the structure of Bi2Sr1.855Ca1.145Cu2O8 was carried out. Data refinements show that the average subcell structure for Bi2Sr1.855Ca1.145Cu2O8 is in the best fit of the space group Fmmm and the structure is described by alternate stacking of SrO-CuO2-Ca-CuO2-SrO slab and a double BiO layers. An oxygen layer sandwiched by the bismuth layers was confirmed.