Dopant Effect on Local Dielectric Properties in Barium Titanate Based Electroceramics Determined by Transmission EELS
Dopant Effect on Local Dielectric Properties in Barium Titanate Based Electroceramics Determined by Transmission EELS
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DOI：
10.1111/j.1151-2916.2002.tb00441.x
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发表时间：
2002-09
影响因子：
3.9
通讯作者：
K. Katti;M. Qian;F. Doğan;M. Sarikaya
中科院分区：
文献类型：
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作者：
K. Katti;M. Qian;F. Doğan;M. Sarikaya
利用低损耗电子能量损失谱（EEL）和透射电子显微镜（TEM）研究了Nb掺杂BaTiO 3电瓷的局域电子激发。的BaTiO 3的电子结构的变化进行了监测作为Nb含量的函数，通过使用Kramers-Kronig分析的低损耗EEL光谱。我们发现，Nb（+5）的价态与Ti（+4）的价态相比，引入了BaTi 1 − xNbxO 3样品的价带和导带态的变化。介电函数的真实的部分Re（1/ε）随着掺杂剂的量的增加而显示出越来越少的负特性，并且价等离子体激元随着Nb的添加（在0.0- 1.8at.%）而显示出“准等离子体激元”特性。此外，随着Nb添加，等离子体激元能量移动（约0.5eV）到更高的值。在钙钛矿样品的局部（纳米尺度）区域中激发的振子强度发生显著变化。这项调查演示了一种方法来定量评估电子性能，在亚微米尺度上，掺杂陶瓷用于电子和电光应用。
Local electronic excitations of Nb-doped BaTiO3 electroceramic were investigated using low-loss electron energy loss (EEL) spectroscopy with a transmission electron microscope. The variations in electronic structure of the BaTiO3 were monitored as a function of Nb content by using Kramers-Kronig analysis of the low-loss EEL spectra. We found that the valence state of Nb (+5) as compared with that of the Ti (+4) introduces changes in the valence and conduction band states of BaTi1−xNbxO3 samples. The real part of the dielectric function, Re(1/ɛ), displays an increasingly less negative character with higher amounts of dopant and the valence plasmon exhibits “quasi-plasmon” characteristics with the addition of Nb (at 0.0–1.8 at.%). Further, the plasmon energy shifts (by about 0.5 eV) to higher values with Nb additions. Significant changes take place in oscillator strengths of excitations in local (nanometer-scale) regions of the perovskite samples. This investigation demonstrates a method to quantitatively assess electronic properties, at the submicrometer scale, of doped ceramics used in electronic and electrooptical applications.