Title :

Structure-property Correlation in Oxide Materials through Aberration-corrected Electron Microscopy

Abstract :

The unprecedented control of the electron beam in the modern electron microscopes allows diffraction from nanometer regions, and conjunctionally being equipped with spectrometers, they can explore chemical information of the material – establishing much coveted structure-property correlations on-the-go. This can be of great interest to a materials chemist, and I will illustrate a couple of examples in that direction from recent works on oxides.

Firstly, the talk will focus on WO3, which exists in a plethora of crystallographic phases. With judicious choice of chemistry, hexagonal and orthorhombic phases can be selectively accessed. Detailed conventional TEM coupled with simulations lead to insights on the operative growth mechanism in that process. Moreover, an epitaxial phase transformation, viz. hexagonal to monoclinic has been observed recently, hitherto unknown in literature. This leads to a possibility of phase-selective ion-intercalation in this material, which will be discussed. Such structural changes have pronounced effect on the electrochromic property of the material. In the next part, I will briefly focus on hexagonal perovskite BaMnO3, wherein reduced Mn-states have been observed on the surface and was established as the reason for its catalytic activity.