Meaning
Diffraction profiles from crystalline powders exhibit widened reflections when structural defects or nanoscale domains are present. In active material diagnostics, peak broadening refers to the increased width of X-ray diffraction peaks, which provides a non-destructive measure of structural properties like grain size and microstrain. This width is typically quantified using the full width at half maximum of the characteristic reflections.
Analytical Calculation
Scherrer’s equation utilizes the broadening effect to estimate crystallite dimensions. When grain boundaries are highly dense, the diffracted beams undergo phase variations that broaden the output profile. Modern analysis must subtract the broadening contribution of the instrument’s optical path to isolate the sample’s true structural characteristics.
Doing so allows researchers to identify atomic-level changes that happen during cycling. Calculations that ignore this instrument bias can underestimate grain dimensions by a factor of two.
Structural Insight
Mechanical degradation shows in diffraction profiles as an increase in peak width. Crystal defects like dislocations and stacking faults create lattice strain, which alters d-spacing values across different grains. When lithium ions are unevenly extracted from the host, localized phase variations further broaden the profiles.
This trend can signal the onset of structural collapse or cathode particle fracture.
Operational Benefit
Analyzing changes in diffraction profiles helps engineers optimize calcination recipes during active material production. It allows fast assessment of material quality and crystalline order before the compound is assembled into cells. Consistently narrow profiles indicate high crystalline phase purity and low structural defect density.
