SAXS and WAXS probe how X-rays are scattered by periodic electron-density modulations in ordered materials. Each ordered phase exhibits a distinctive set of Bragg peaks whose positions follow characteristic ratios determined by the symmetry of the lattice.
Phase identification relies on comparing the expected reflections (their q-positions and intensity ratios) with the experimental scattering pattern. Once a match is established, the technique provides quantitative structural parameters, including:
- Phase symmetry and identification, based on the scattering peak sequence (e.g., lamellar, hexagonal, cubic)
- Unit cell parameters, derived from peak positions according to the lattice geometry
- Degree of order, inferred from peak sharpness and multiplicity
- Phase coexistence or transitions, visible from the appearance or disappearance of symmetry-specific reflections
Figure 1. Experimental WAXS data (black) are compared with the expected Bragg peak positions of the LaB₆ crystalline phase (blue), and a peak-fitting model (yellow) is applied to extract lattice parameters and confirm phase purity. The close agreement between measured and calculated intensities demonstrates robust identification of the crystalline phase.
SAXS is sensitive to nanometer-scale periodicities, while WAXS extends this capability to smaller lattice spacings, enabling combined analysis when necessary.
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