Dopant Effect on Local Dielectric Properties in Barium Titanate Based Electroceramics Determined by Transmission EELS

Abstract

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‐Krönig 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.