Effects of Fe and Ni on Crystal Structure of Zr_4Co_4Si_7(V—Phase)
Mao Jianfu Ye Hengqiang Ning Xiaoguang He Lianlong Yang Dezhuang (Laboratory of Atomic Imaging of Solids ,Institute of Metal Research,Chinese Academy of Science,Shenyang 110015) (*School of Materials Science and Engineering,Harbin Institute of Technology,Harbin 15001)
High resolution transmission electron microscope (HRTEM)technique combined with computer image simulation, which reveals microstructural features of materials at atomic level, is now used to study the closedpacked structures of Zr_4Co_4Si_4 (V phase)compound. The experimental results show that Zr_4Co_4Si_7 is a body centered tetragonal structure with space group I4/mmm. It's lattice constants a=1. 2935nm and c=0.509nm. It is found that under the condition of adding the fourth constitutional elements Fe or Ni, the vectors of the unit cell in Zr_4Co_4Si_7 are contracted in one dimension (along a axis) and extended in two dimensions (along b and c axes). They are a=1. 2930nm, b=1. 3384nm, c=0.5094nm for Zr_4 (Co_(3.5) Fe_(0.5)) Si_7 and a=1.2935nm, b=1.3256nm, c=0.5094nm for Zr_4(Co_(3.5)Ni_(0.5))Si_7, respectively. However, the lattice type and relative atomic positions are not changed in their crystal structures, remaining with the structure of V phase.