Fig. 3.

a Analysis of NIST SRM 470 (K411 glass) as a flat, highly polished bulk sample (final polish with 100 nm alumina) using the k-ratio protocol with SDD-EDS measurements and NIST DTSA-II. Plot of Fe (normalized weight percent) vs. Mg (normalized weight percent) for 20 randomly selected analyses. Note the outlier (circled). b Analysis of NIST SRM 470 (K411 glass) as a flat, but slightly scratched bulk sample (scratches remaining after 1 µm diamond polish) using the k-ratio protocol with SDD-EDS measurements and NIST DTSA-II. Plot of Fe (normalized weight percent) vs. Mg (normalized weight percent) for 20 randomly selected analyses