Study on atomic and electronic structures of ceramic materials using spectroscopy, microscopy, and first principles calculation

Abstract

In this review, following two topics are introduced: 1) experimental and theoretical electron energy loss (EEL) near edge structures (ELNES) and X-ray absorption near edge structures (XANES), and 2) atomic and electronic structure analysis of ceramic interface by combing spectroscopy, microscopy, and first principles calculation. In the ELNES/XANES calculation, it is concluded that inclusion of core-hole effect in the calculation is essential. By combining high energy resolution observation and theoretical calculation, detailed analysis of the electronic structure is achieved. In addition, overlap population (OP) diagram is used to interpret the spectrum. In the case of AlN, sharp and intense first peak of N-K edge is found to reflect narrow dispersion of the conduction band bottom. By applying ELNES and the OP diagram to Cu/Al 2 O 3 heterointerface, it is revealed that intensity of prepeak in O-K edge is inverse proportional to interface strength. The relationships between atomic structure and defect energetics at SrTiO 3 grain boundary are also investigated, and reveal that the formation behavior of Ti vacancy is sensitive to the structural distortion. In addition, by using state-of-the-art spectroscopy, microscopy, and first principles calculations, atomic scale visualization of fluorine dopant in LaFeOAs and first principles calculation of HfO 2 phase transformation are demonstrated.©2011 The Ceramic Society of Japan. All rights reserved.Key-words : Structure-property relationships, EELS/XAFS, TEM/STEM, First principles calculation [Received February 14, 2011; Accepted March 8, 2011] General introductionCeramic materials have been widely used in mechanical and functional applications, and now be indispensable materials to sustain modern technologies. However, much higher performance and higher reliability are required to the ceramic materials to achieve further technology developments. In case of electroceramics, such as multi-layer ceramic capacitor and varistor, the size of their grains in electric devices becomes smaller and smaller, ca. 1¯m or less, and thus further property improvements of each grain and grain boundary are desired. To achieve this, clarification of atomic and electronic structures and finding the way to improve their properties are indispensable.Nowadays, atomic and electronic structure analysis with high resolutions and high accuracies is possible by the grace of recent instrumental and computational developments. In this review, atomic and electronic structure analysis of ceramic materials by combining electron energy loss spectroscopy (EELS), transmission electron microscopy (TEM), and first principles calculation are demonstrated. Experimental and theoretical EELS are discussed in Sec. 2, 1),2) and their applications to ceramic interfaces, Cu/Al 2 O 3 hetero interface 3) and SrTiO 3 grain boundary, 4)6) are presented in Sec. 3. At the end, state-of-the-art microscopy, spectroscopy, and first principles calculation are introduced. Theoretical calculation of ELNES and XANESNear ed...

Density Functional Theory for ELNES in STEM-EELS

“…8.11. Using this OP diagram, the relationships between the spectral features and the materials properties can also be found, such as the relationships with the interface strength (Mizoguchi et al, 2006b) and electron effective mass (Mizoguchi, 2009(Mizoguchi, , 2011. This is an important advance in the interpretation of EELS.…”