Direct electron detection for EBSD of low symmetry & beam sensitive ceramics
Nicolò Maria della Ventura, Andrew R. Ericks, McLean P. Echlin, Kalani Moore, Tresa M. Pollock, Matthew R. Begley, Frank W. Zok, Marc De Graef, Daniel S. Gianola
Abstract
Electron backscatter diffraction (EBSD) is a powerful tool for determining the orientations of near-surface grains in engineering materials. However, many ceramics present challenges for routine EBSD data collection and indexing due to small grain sizes, high crack densities, beam and charge sensitivities, low crystal symmetries, and pseudo-symmetric pattern variants. Micro-cracked monoclinic hafnia, tetragonal hafnon, and hafnia/hafnon composites exhibit all such features, and are used in the present work to show the efficacy of a novel workflow based on a direct detecting EBSD sensor and a state-of-the-art pattern indexing approach. At 5 and 10 keV primary beam energies (where beam-induced damage and surface charge accumulation are minimal), the direct electron detector produces superior diffraction patterns with 10x lower doses compared to a phosphor-coupled indirect detector. Further, pseudo-symmetric variant-related indexing errors from a Hough-based approach (which account for at least 4%-14% of map areas) are easily resolved by dictionary indexing. In short, the workflow unlocks fundamentally new opportunities to characterize materials historically unsuited for EBSD. • A novel EBSD workflow allows to characterize low-symmetry, charge-sensitive ceramics. • DED yields superior EBSP quality at low keV compared to traditional detectors. • DED yields high-resolution maps revealing fine microstructural features as twins. • At low keV, dictionary indexing surpasses Hough indexing in orientation accuracy. • Hough indexing errors in hafnia vary with voltage due to pseudo-symmetric variants.