A method for a column-by-column EELS quantification of barium lanthanum ferrate.

Area of Science:

• Materials Science
• Analytical Chemistry
• Solid-State Physics

Background:

• Scanning Transmission Electron Energy Loss Spectroscopy (STEM-EELS) offers atomic-scale compositional analysis of crystalline materials.
• Quantitative chemical analysis in STEM-EELS is challenged by zone axis conditions, causing signal overlap from adjacent atomic columns.

Purpose of the Study:

• To develop a procedure for precise quantitative chemical analysis of elements within equivalent atomic columns using STEM-EELS elemental maps.
• To determine the concentration of barium and lanthanum in the A-sites of Ba1.1La1.9Fe2O7, a second-order Ruddlesden-Popper phase.

Main Methods:

• Utilized STEM-EELS elemental mapping to analyze the distribution of barium and lanthanum.
• Developed a quantification technique that substitutes inelastic scattering cross sections with experimentally derived parameters.
• Incorporated inelastic multislice simulations to account for channeling/de-channeling effects and determine atomic column occupancies.
• Integrated EELS quantification results as prior information into X-ray Diffraction (XRD) Rietveld refinement.

Main Results:

• Successfully determined the concentration of barium and lanthanum within individual atomic columns of Ba1.1La1.9Fe2O7.
• The developed method effectively addressed the limitations imposed by zone axis conditions in STEM-EELS.
• The combined approach of EELS and XRD enabled accurate differentiation between barium and lanthanum occupancies.

Conclusions:

• The presented procedure enables reliable quantitative chemical analysis at the atomic scale using STEM-EELS.
• This method enhances the accuracy of elemental mapping, particularly for distinguishing between elements in equivalent crystallographic sites.
• The integration with XRD provides a robust approach for complex material characterization.