This application example demonstrates the use of the novel Advanced Phase ID tool for the characterization of a complex mineral sample. Not only does Advanced Phase ID assist in finding all phases in a sample in a semi-automated procedure, it also helps to improve indexing quality by always determining the best fitting phase in the installed databases. As an additional benefit, Bruker's pattern streaming method allows to perform most of the analysis offline, minimizing SEM occupation time.
The sample discussed here is a polished segment of a mineralogical sample (data courtesy Dr. Angela Halfpenny, CSIRO, Perth, Australia) that was analyzed using EBSD and EDS simultaneously. The backscattered electron image and the pattern quality map already reveal that the sample is highly structured and the grain sizes and shapes already indicate the presence of several phases. The first part of the analysis procedure is straightforward:
- Acquire an EDS spectrum and an EBSP at the same position
- Search the database for candidate phases; in this case (containing Fe, O) it results in 289 entries!
- Perform automatic or interactive band detection
- Subsequently the software tries to index using all 289 entries (requires ~ 10 s)
- Solutions are classified based on quality of fit
- The best fitting phase file is added to the phase list
- Perform data acquisition
All subsequent steps, meaning the determination of all remaining phases can be performed online as well as offline, using the acquired data set – the Magnetite phase (yellow) was already determined above:
- Select a point in the map, where no phase has been determined and display pattern and spectrum
- Perform Advanced Phase ID, in this case Ilmenite has been determined
- Re-index the whole map (requires no more than 50 s for the 1000x750 pixels map)
- Repeat steps 1 and 2 until all phases have been found, step 3 does not necessarily have to be performed after every new phase has been found
In the end the user spent less than an hour at the SEM and approximately 20 minutes for the offline dataset completion. In total a record-breaking number of 10 phases were found: Magnetite (yellow), Ilmenite (green), Pyrrotite (orange), Apatite (purple), Quartz (red), Augite (pink), Clinohyperstene (dark blue), Plagioclase (brown-grey), Tremolite (bright blue) and Clinochlore ("Chamosite", dark green). As the latter is a product of alteration and therefore presents poor diffraction patterns, it is a contributor to the 5.13 % zero solutions, together with the porosity.