Atomic DualEELS analysis of CaFeO2,5 Brownmillerite structure—Investigating the presence of oxygen vacancies
Paolo Longo, Ph.D., Gatan, Inc. Sample courtesy of Professor Ramachandra Rao at Indian Institute of Technology, Chennai Madras, India Microscope courtesy of Dr. Giuseppe Nicotra at IMM-CNR, Catania, Italy

Atomic DualEELS analysis of CaFeO2,5 Brownmillerite structure—Investigating the presence of oxygen vacancies

Fe-O atoms are arranged in alternating tetrahedral and octahedral planes that can be distinguished looking at the fine structure of the O K-edge at 532 eV. Hybridization between the O and Fe orbitals is different depending on the way the atoms are arranged, and changes can be seen in the O K-edge at 532 eV in the EELS spectrum.

Methods

probe corrected ARM 200F TEM/STEM microscope
C-FEG emission gun
GIF Quantum® ER system
voltage: 200 kV
data taken in STEM mode
EELS low-loss spectrum (0–500 eV) exposure time: 0.2 ms
EELS core-loss spectrum (250–750 eV) exposure time: 50 ms
beam current: 70 pA
total exposure time: <2 min