Large-Area Quantitative Phase Mapping
move the beam between pixels would be required, indicating an estimated total time to identify and phase-type the grains within this large area would be 89 seconds. T us, electron image + spot mode EDS typing may be expected to run approximately 3 times faster than large-area COMPASS phase mapping. However, this basic typing provides no quantitative analysis of each grain, thereby leaving open the opportunity for serious omission of phases and misclassifi cation of phases in many of the grains. COMPASS phase mapping, while taking somewhat longer, provides a more accurate and reliable means of phase detection and determination. T e two techniques provide a diff erent approach and a trade-off between information speed (that is, how fast one can collect the data) and information quality (that is, how accurately the analysis can be performed).
Conclusion
Figure 9 : Large-area COMPASS phase map of ceramic composite. Image width = 0.98 mm. See phase legend in Table 3 .
Table 3 : Phase analysis of a ceramic composite shown in Figures. 8 and 9 showing the 11 mineral phases color coded to Figure 9 .
Phase Carbon matrix Barite Antimony sulfide
Copper iron disulfide
Fe oxide Calcium sulfate Aluminum silicate Quartz
Magnesium aluminum oxide
Potassium aluminum silicate Zinc sulfide
Magnesium iron sulfate
44
Area % 40.42
23.3 11.49 9.61 6.84 3.37 1.71 1.12 1.08 0.57 0.47 0.03 Color legend
For many decades, the SEM has been a mainstay scientifi c instrument for materials analysis. T e addition of EDS nearly 50 years ago enhanced the capabilities of the SEM and led to progressively more detailed materials characterization. With the advent of SDD X-ray detector technology and spectral imaging techniques, EDS analysis in the SEM has evolved to include EDS X-ray element maps, large-area elemental analysis with stage movement for multi-frame acquisition, and automated EDS analysis of distinct phase regions determined by grayscale brightness/contrast thresholding. With principle component analysis as an engine for EDS phase mapping, ultra-large-area quantitative phase mapping with high information content can be added to this impressive list of EDS advances for SEM-based materials science research.
References [1] K T ompson , “Silicon Driſt Detectors,” T ermo Fisher Scientifi c white paper WP52342 (2013) https://tools. thermofi
sher.com/content/sfs/brochures/TN52342_ E_0512M_SiliconDriſt _H.pdf .
[2] Y Gu , Journal of Minerals & Materials Characterization & Engineering 2 ( 1 ) ( 2003 ) 33 – 41 .
[3] D Pirrie et al ., Geological Society , London , Special Publications , 232 ( 2004 ) 123 – 36 .
[4] PG Kotula et al ., Microsc Microanal 12 ( 2006 ) 538 – 44 . [5] D West , “Principal Component Analysis in EDS: T e COMPASS Algorithm”, T ermo Fisher Scientifi c white paper WP52773 (2015)
http://www.thermofi
sher.com/ pathfi nder .
[6] J Shlens , “A tutorial on principal component analysis ,” arXiv: 1404 . 1100 ( 2014 )
https://arxiv.org/abs/1404.1100 .
[7] C van Hoek , Microscopy Today 24 ( 5 ) ( 2016 ) 12 – 20 . [8] AM Hagni , “Fine-particle characterization by rietveld QXRD, CLM, and SEM-EDS phase mapping ” J Microsc 54 ( 2002 ) 24 – 26 .
[9] A Ruffell et al ., Geological Society, London , Special Publications, 384 ( 2013 ) 147 – 61 .
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www.microscopy-today.com • 2017 March
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