中国物理B ›› 2018, Vol. 27 ›› Issue (6): 60503-060503.doi: 10.1088/1674-1056/27/6/060503

所属专题: TOPICAL REVIEW — Electron microscopy methods for emergent materials and life sciences

• TOPICAL REVIEW—Electron microscopy methods for the emergent materials and life sciences • 上一篇    下一篇

Chemical structure of grain-boundary layer in SrTiO3 and its segregation-induced transition: A continuum interface approach

Hui Gu(顾辉)   

  1. School of Materials Science & Engineering, Materials Genome Institute, Shanghai University, Shanghai 200444, China
  • 收稿日期:2018-04-08 修回日期:2018-05-14 出版日期:2018-06-05 发布日期:2018-06-05
  • 通讯作者: Hui Gu E-mail:gujiaoshou@shu.edu.cn
  • 基金资助:

    Project supported by the National Natural Science Foundation of China (Grant No.51532006),the Fund from Shanghai Municipal Science and Technology Commission (Grant No.16DZ2260600),the 111 Project of the Ministry of Education,and the Fund from the National Bureau of Foreign Experts (Project No.D16002).

Chemical structure of grain-boundary layer in SrTiO3 and its segregation-induced transition: A continuum interface approach

Hui Gu(顾辉)   

  1. School of Materials Science & Engineering, Materials Genome Institute, Shanghai University, Shanghai 200444, China
  • Received:2018-04-08 Revised:2018-05-14 Online:2018-06-05 Published:2018-06-05
  • Contact: Hui Gu E-mail:gujiaoshou@shu.edu.cn
  • Supported by:

    Project supported by the National Natural Science Foundation of China (Grant No.51532006),the Fund from Shanghai Municipal Science and Technology Commission (Grant No.16DZ2260600),the 111 Project of the Ministry of Education,and the Fund from the National Bureau of Foreign Experts (Project No.D16002).

摘要:

Grain-boundary (GB) structures are commonly imaged as discrete atomic columns, yet the chemical modifications are gradual and extend into the adjacent lattices, notably the space charge, hence the two-dimensional defects may also be treated as continuum changes to extended interfacial structure. This review presents a spatially-resolved analysis by electron energy-loss spectroscopy of the GB chemical structures in a series of SrTiO3 bicrystals and a ceramic, using analytical electron microscopy of the pre-Cs-correction era. It has identified and separated a transient layer at the model Σ5 grain-boundaries (GBs) with characteristic chemical bonding, extending the continuum interfacial approach to redefine the GB chemical structure. This GB layer has evolved under segregation of iron dopant, starting from subtle changes in local bonds until a clear transition into a distinctive GB chemistry with substantially increased titanium concentration confined within the GB layer in 3-unit cells, heavily strained, and with less strontium. Similar segregated GB layer turns into a titania-based amorphous film in SrTiO3 ceramic, hence reaching a more stable chemical structure in equilibrium with the intergranular Ti2O3 glass also. Space charge was not found by acceptor doping in both the strained Σ5 and amorphous GBs in SrTiO3 owing to the native transient nature of the GB layer that facilitates the transitions induced by Fe segregation into novel chemical structures subject to local and global equilibria. These GB transitions may add a new dimension into the structure-property relationship of the electronic materials.

关键词: space charge layer, strontium titanate bicrystal, spatially-resolved electron energy-loss spectroscopy, interfacial transition

Abstract:

Grain-boundary (GB) structures are commonly imaged as discrete atomic columns, yet the chemical modifications are gradual and extend into the adjacent lattices, notably the space charge, hence the two-dimensional defects may also be treated as continuum changes to extended interfacial structure. This review presents a spatially-resolved analysis by electron energy-loss spectroscopy of the GB chemical structures in a series of SrTiO3 bicrystals and a ceramic, using analytical electron microscopy of the pre-Cs-correction era. It has identified and separated a transient layer at the model Σ5 grain-boundaries (GBs) with characteristic chemical bonding, extending the continuum interfacial approach to redefine the GB chemical structure. This GB layer has evolved under segregation of iron dopant, starting from subtle changes in local bonds until a clear transition into a distinctive GB chemistry with substantially increased titanium concentration confined within the GB layer in 3-unit cells, heavily strained, and with less strontium. Similar segregated GB layer turns into a titania-based amorphous film in SrTiO3 ceramic, hence reaching a more stable chemical structure in equilibrium with the intergranular Ti2O3 glass also. Space charge was not found by acceptor doping in both the strained Σ5 and amorphous GBs in SrTiO3 owing to the native transient nature of the GB layer that facilitates the transitions induced by Fe segregation into novel chemical structures subject to local and global equilibria. These GB transitions may add a new dimension into the structure-property relationship of the electronic materials.

Key words: space charge layer, strontium titanate bicrystal, spatially-resolved electron energy-loss spectroscopy, interfacial transition

中图分类号:  (Interface and surface thermodynamics)

  • 05.70.Np
68.35.Dv (Composition, segregation; defects and impurities) 68.37.Ma (Scanning transmission electron microscopy (STEM)) 81.70.Jb (Chemical composition analysis, chemical depth and dopant profiling)