Use of electron backscatter diffraction patterns to determine the crystal lattice. Part 2. Offset corrections

Area of Science:

• Materials Science
• Crystallography
• Electron Diffraction

Background:

• Kikuchi band width analysis is a common method for determining lattice parameters.
• First derivative band profile analysis systematically underestimates the true Bragg angle, leading to errors in lattice parameter calculations (Δa/a).
• This offset is particularly significant for high mean atomic number (Z) materials.

Purpose of the Study:

• To propose and validate corrections for the systematic underestimation of Bragg angles in Kikuchi band width measurements.
• To develop a predictive model for the offset (Δa/a) based on material properties.
• To improve the accuracy of lattice parameter determination using Kikuchi patterns.

Main Methods:

• Dynamical simulations of Kikuchi patterns were performed.
• Analysis of band widths and their first derivatives was conducted.
• A correction function, Δa/a = f(Z), incorporating mean atomic number and unit-cell volume was developed and tested.

Main Results:

• Systematic underestimation of Bragg angles leads to lattice parameter offsets (Δa/a) up to 8% for high-Z materials.
• The offset decreases linearly with decreasing mean atomic number (Z).
• The proposed correction, considering Z and unit-cell volume, reduces the offset-corrected lattice parameter deviation to <1.5% for simulated patterns.
• Lattice parameter ratios and interaxial angles (α, β, γ) remain unaffected by the offset.

Conclusions:

• The proposed correction method significantly enhances the accuracy of lattice parameter determination from Kikuchi band widths.
• The developed offset prediction function (Δa/a = f(Z)) provides a reliable way to compensate for measurement errors.
• This method is valuable for analyzing both known and unknown crystalline phases, even when only the maximum atomic number (Zmax) is available.