High-Precision Measurement of Temperature Factors for NiAl by Convergent-Beam Electron Diffraction

Convergent-beam electron diffraction is applied to measure the temperature factors of the intermetallic phase NiAl with high accuracy. The patterns are recorded in an energy-filtering transmission electron microscope at zero energy loss using a slow-scan CCD camera. The specimens were tilted in systematic row orientation. In this new approach, data are extracted from the bright-field disc as well as from several high-order dark-field discs along line scans. The temperature factors are determined by fitting Bloch-wave simulations to the intensity profiles. The harmonic approximation for temperature factors is used. For B2-phase NiAl, mean thermal displacements u(Ni) = 5.5 ± 0.1 and u(Al) = 5.7 ± 0.1 pm are obtained at 100 K. A very detailed error analysis is given, and stochastic and systematic errors are discussed and quantified.