National Changhua University of Education Institutional Repository : Item 987654321/14104
English  |  正體中文  |  简体中文  |  全文笔数/总笔数 : 6507/11669
造访人次 : 30066363      在线人数 : 614
RC Version 3.2 © Powered By DSPACE, MIT. Enhanced by NTU Library IR team.
搜寻范围 进阶搜寻

jsp.display-item.identifier=請使用永久網址來引用或連結此文件: http://ir.ncue.edu.tw/ir/handle/987654321/14104

题名: Composition-Controlled Metal-Nonmetal Transition in La2-xSrxNiO4-δ
作者: Liu, Chia-Jyi;Mays, M. D.;Cowan, D. O.;Sanchez, M. G.
贡献者: 物理學系
日期: 1991-05
上传时间: 2012-09-10T06:11:01Z
出版者: American Chemical Society
摘要: Materials with the general composition La2,Sr,Ni04-l retain the perovskite-related structure of space
group Nlmmm up to x = 1.50. They undergo a composition-dependent metal-nonmetal transition in
electrical conductivity. The composition parameters x and 6 determine the conductivity type. For x <
1 the materials are nonmetals. For x > 1.1 metallic conductivity is observed that persists to a limit of
at least x = 1.50 if the oxygen deficiency 6 is low. For compositions near the transition the conductivity
type is also dependent on 6. Metallic samples become nonmetals upon heating in flowing Ar at 1000 "C,
which revert to metals upon oxidation in O2 also at 1000 "C. All nonmetal-to-metal transitions are
accompanied by a change in color from black to reddish brown. The Ni average valence u was determined
from the metals composition and iodometric titration data. The 6 value was calculated from u by using
the equation 6 = 0.5~+ (1 - 0.5u), which was derived by using a formal valence convention. Both v and
6 increase monotonically with x in the range 0 5 x I 1.5. A phase diagram is proposed for the metal-nonmetal
transition in which the boundary is given by 6 = 0.5~- 0.51, which corresponds to u i= 3.02. No stoichiometric
214 nickelate (6 = 0) could be prepared in the metallic region, and no superconductive transition was observed
in any material down to -3 K.
關聯: Chemistry of Materials, 3(3): 495-500
显示于类别:[物理學系] 期刊論文

文件中的档案:

档案 大小格式浏览次数
index.html0KbHTML651检视/开启


在NCUEIR中所有的数据项都受到原著作权保护.

 

DSpace Software Copyright © 2002-2004  MIT &  Hewlett-Packard  /   Enhanced by   NTU Library IR team Copyright ©   - 回馈