P. Raval, N. P. Joshi, P. R. Pansara
Dec 1, 2018
Abstract The electronic structures of stoichiometric, single phase, coarse-grained CaCu3-xTi4-xFe2xO12 (x = 0.0, 0.1, 0.3, 0.5 and 0.7) polycrystalline ceramics have been investigated using powerful X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopic measurements, performed near Ti L3,2 and Ti K- edges, registered at 300 K. The absence of pre-edge structures in Ti L3,2 – edge are indicative of a departure from octahedral cubic symmetry, while the observed small increase in the intensity of absorption peaks has been attributed to increasing spin-orbital coupling with increasing Fe-content (x) in the system. The presence of a pre-edge feature in Ti K- edge spectra confirms the presence of octahedrally coordinated Ti4+ ions in the system. The EXAFS spectra measured at Ti K- edge indicate the first shell Ti—O bond distances to be nearly 1.56 A in the sample without Fe. With the increase in the Fe- concentration (x), the Ti-O distance shows a slight reduction. The second shell Ti-Ca bond distance comes out to be nearly 2.6 A which decreases with an increase in the Fe - concentration.