Pair distribution function (PDF) analysis of mesoporous α-Fe2O3 and Cr2O3

Area of Science:

• Materials Science
• Nanotechnology
• Solid-State Chemistry

Background:

• Mesoporous metal oxides, such as alpha-Fe2O3 and Cr2O3, possess ordered pore structures and crystalline pore walls.
• Characterizing these materials requires understanding their unique structural properties.

Purpose of the Study:

• To measure and compare the atomic pair distribution functions of bulk and mesoporous alpha-Fe2O3 and Cr2O3.
• To determine the extent of long-range structural coherence in these novel mesoporous materials.
• To investigate the impact of mesoporosity on atomic-level structural order.

Main Methods:

• Atomic pair distribution function (PDF) measurements.
• Analysis of PDF data for both bulk and mesoporous samples.
• Box-car analysis to probe structural coherence at different length scales.

Main Results:

• Estimated long-range structural coherence of approximately 125 Å for alpha-Fe2O3 and 290 Å for Cr2O3.
• Significant deviation of mesoporous samples from bulk counterparts observed above approximately 40 Å.
• Pore-induced voids in pair-correlations were identified as the cause for disrupted long-range order.

Conclusions:

• Mesoporous metal oxides exhibit distinct structural characteristics compared to their bulk forms.
• The presence of pores significantly disrupts long-range atomic order in these materials.
• Understanding these structural deviations is crucial for applications of mesoporous metal oxides.