Space‐Charge Distribution across Internal Interfaces in Electroceramics Using Electron Holography: I, Pristine Grain Boundaries
Space‐Charge Distribution across Internal Interfaces in Electroceramics Using Electron Holography: I, Pristine Grain Boundaries
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DOI：
10.1111/j.1151-2916.1997.tb02954.x
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发表时间：
2005-01
影响因子：
3.9
通讯作者：
V. Ravikumar;R. Rodrigues;V. Dravid
中科院分区：
文献类型：
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作者：
V. Ravikumar;R. Rodrigues;V. Dravid
透射式高能电子全息术被用来定量地确定多晶钛酸锶中电势、电场的大小、符号和空间范围以及电活性晶界上的电荷和应力场的分布。所用的多晶压坯分别是Fe的体相掺杂和Gb的Mn的掺杂，在非平衡状态下扩散到其中。全息照相结果揭示了带负电荷的GBs和伴随的正空间电荷，表明Mn以受主掺杂的形式存在于Ti位上，在GBs处产生了负束缚电荷。在不同的带隙中观察到了很大的电活性不均一性；一些带区表现出很高的肖特基势垒，而另一些带区具有很小的势垒。对形成GB电荷和空间电荷的束缚电荷和补偿自由电荷的分布进行了估算。由于国标两侧电场的作用，束缚电荷经历了一个向外的应力场。从这些全息术结果可以得到双肖特基势垒的高度、德拜长度以及束缚电荷和空间电荷在GB处的空间范围。结果还提供了缺陷密度的定量测量以及静应力场对晶格弛豫的贡献，并为GB提供了一个点缺陷模型。
Transmission high-energy electron holography has been utilized to quantitatively determine the magnitude, sign, and spatial extent of the electrical potential, electric field, as well as the charge and stress field distributions across electrically active grain boundaries (GBs) in polycrystalline SrTiO3. The polycrystalline compacts utilized were bulk-doped with Fe and GB-doped with Mn, which is diffused into them under a nonequilibrium situation. The holography results reveal negatively charged GBs with associated positive space-charge, indicating that Mn resides as an acceptor dopant on the Ti site, creating a negative bound charge at the GBs. A large heterogeneity in the electrical activity is observed among various GBs; while some GBs show high Schottky barriers, others have very small barriers. The distribution of the bound charge and the compensating free charge, which together contribute to the formation of GB charge and space-charge, has been estimated. The bound charge experiences an outward stress field due to the force of the electric field on either side of the GB. The height of the double Schottky barrier, the Debye length, as well as the spatial extent of the bound charge and space-charge at the GB are derived from these holography results. The results also provide a quantitative measure of the defect densities as well as of the contribution of the electrostatic stress field to the lattice relaxation at the GBs and yield a point defect model for the GB.