With the help of the robust software program, Spectrum Match, users can search a custom built spectrum library to locate similar spectra. This minimizes the difficulty of identifying differences and similarities between spectra and makes it much simpler to identify unknowns by comparing them to a set of likely candidates.
Spectrum Match is a flexible tool with a wide range of uses, such as:
- Process control - By combining phase mapping and spectrum matching, changes in distribution and composition can be immediately detected
- Reverse engineering - A library of common components included in the material can be used to compare material constituents
- Failure analysis and quality control - Defects can be compared to a collection of potential contaminants
Figure 1. Spectrum matching uses either Chi-Square fit on the spectrum intensities or Chi-Square fit on the concentration results. Image Credit: EDAX
Figure 2. Spectrum extracted from the map visibly and numerically identifies this phase as SbS with a much higher fit % compared to CaSO4, even though they contain common elements. Image Credit: EDAX
By directly comparing concentrations or spectra, a chi-squared goodness of fit test matches the active spectrum to those identified in the library file (Figure 1). Due to the adjustable match sensitivity, the user has complete control over the match results, ranging from exactly similar to within spitting distance.
The prospective matching spectra are superimposed on the original spectrum. The match percentage provides a numerical assessment of how close or dissimilar the spectra are and a visual illustration of the differences.
A sample spectrum with two overlay spectra is shown in Figure 2 with match values of 81.53% for SbS and 62.64% for CaSO4. A short visual examination reveals that the Si, Ti, Ba, and Zr contents are where the differences between the sample and the spectrum with the best match can be detected.
The spectrum search tool makes creating a library of spectrum matches simple. The user can manually select particular project nodes or apply filters to find spectra with the needed properties to explore the entire database of stored spectra on the system. The filters consist of:
- Presence of given elements (with range in atomic %, weight %, or net intensity)
- kV used
- Sample name
- Acquisition date
The spectra are saved to a Spectrum Match library file after being chosen, which can then be shared between users and systems. It is possible to add all information in the system database to a Spectrum Match library file.
Smart Materials and Minerals Library
There are 150 entries for common metal standard alloys and minerals in the EDAX Smart Materials and Minerals Library. The library contains:
- 90 steel spectra
- Tool steels
- Stainless steels
- Carbon steels
- Alloy steels, Ni-based steels, Cu-based alloys
- 50+ silicates and other geological standard materials