水热反应条件对BaTiO3纳米晶形成的影响及其原子尺度表面结构

本文报道了水热反应条件对BaTiO3纳米晶形成的影响，尤其是其原子尺度的表面结构。研究结果表明，Ba/Ti摩尔比较大的前驱体溶液中，易获得立方状大尺寸（～260nm）的BaTiO3纳米晶体；而采用乙二醇作为水热反应介质，可获得小尺寸弱圉聚的BaTiO3纳米晶（与纯水溶液或水-乙二醇的混合液相比较）。立方状或长方体状的BaTiO3纳米晶外表面被{100}晶面所包围，{110}晶面条纹与纳米晶体的边界相交呈45°角。在粗糙的BaTiO3纳米晶表面，常可观察到台面台阶扭折（terrace—ledge—kink）的表面结构，台面（terrace）和台阶（1edge）位于{100}晶面。由于表面结构的重构，{110}晶面通常被分解成由许多小的{100}晶面相连接而成的扭折结构。而在球状的BaTiO3纳米晶边缘，没有观察到表面台阶结构。

Influences of reactive conditions on the formation of hydrothermal BaTiO3 nanocrystals and their atomic-scale surface structures

The influences of reactive conditions upon the formation of BaTiO3 （BT） nanocrystals via hydrothermal process was investigated, especially on their atomic-scale surface microstructures. The results showed that large Ba/Ti molar ratios in the precursors could lead to large nanocrystals with a cubic morphology. Small nanocrystals with a weak agglomeration behavior were observed in the products synthesized via solvothermal process using ethylene glycol （EG） as reaction medium, in comparison to using either pure water or water-EG mixed solution as reactive medium. The BT nanocrystals with either cubic or rectangular shapes, are bounded by their {100} facets, as confirmed by the {110} lattice fringes intersecting with their edges at 45°. A terrace-ledge-kink （TLK） surface structure is frequently observed at the edges of the rough nanocrystals, and surface steps lying on the {100} planes are clearly observed. The {110} surfaces were found to be reconstructed and composed of the corners bound by the {100} mini-faces. However, in the spherical BT nanocrystals, no surface steps were observed at their edges.