A tool for assisting phase identification by micro‐Raman spectroscopy

Abstract

Although powder X‐ray diffraction is often the primary choice for the analysis of naturally occurring materials, the robust identification of individual components in a complex mixture is usually a challenging task, and other analytical tools are often needed to allow unequivocal phase identification. Among these techniques, the spatial resolution provided by micro‐Raman spectroscopy has proved to be invaluable as a complementary technique to X‐ray diffraction analysis. Accordingly, in this work we present a tool for assisting phase identification by micro‐Raman spectroscopy. This tool was implemented with a graphical user interface, thus facilitating all stages of analysis, including multiple spectra reading, interpolation, and baseline correction, as well as pure component spectra determination by multivariate curve resolution analysis and their identification against an open‐access database. To exemplify the proposed approach, the mineral phases present in an igneous rock from the Serra Geral Formation, Brazil, were identified and then used as the starting point for a full Rietveld refinement of the corresponding X‐ray diffraction pattern. Some phases not identified by micro‐Raman spectroscopy could then be identified by conventional search‐match on the difference X‐ray diffraction pattern. Further testing of the tool yielded the correct identification of the mineral phases used to create noise‐added computer‐generated multiphase Raman spectra. Although the tool developed in this work is currently designed to be used with a database of Raman spectra of minerals, it can be easily modified to be used in a more general context, provided a suitable database of Raman spectra is available.

Effect of iron on the microstructure of basalt glass‐ceramics obtained by the petrurgic method

“…The X‐ray powder diffraction pattern of rock B was compared to that of a basaltic rock also from SGF previously reported by Ramos et al 34 . Figure 1 shows the powder pattern for these two samples.…”

“…Phase identification was performed using DIFFRAC.EVA (version 4.0, Bruker). The procedure to estimated amounts of crystalline phases in sample B was based on the Rietveld analysis of the X-ray powder diffraction pattern by Ramos et al 34 The rock chemical composition was determined by energy dispersive X-ray fluorescence (EDX-7000, Shimadzu). The previously dried powder sample (110 • C for 2 h) was evaluated in a sample holder sealed with mylar film.…”

“…The X-ray powder diffraction pattern of rock B was compared to that of a basaltic rock also from SGF previously reported by Ramos et al 34 Figure 1 shows the powder pattern for these two samples. From the similarity between F I G U R E 1 X-ray powder diffraction patterns of the basalt used in this work (B) and the basalt from Ramos et al 34 them, which exhibit Bragg peak at the same positions and intensities, the same crystalline phases, as well as the relative amounts, were considered to be the same in the present sample as in the basalt from Ramos et al 34 Table 1 shows the crystalline phases and the corresponding estimated amount by mass, as well as the chemical formula and the magnetism type of each phase present in the basalt rock. Generally, the Fe 2+ cation is present in olivines, pyroxenes, ilmenite, mica, and amphiboles, while the Fe 3+ cation is present in phases such as magnetite and hematite.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part XIII

“…Ramos et al presented a tool for assisting phase identification by micro‐Raman spectroscopy. Although the tool developed in this work is currently designed to be used with a database of Raman spectra of minerals, it can be easily modified to be used in a more general context, provided a suitable database of Raman spectra is available . Register and co‐workers used SERDS for the detection of SERS‐encoded gold nanostar probes.…”

“…Although the tool developed in this work is currently designed to be used with a database of Raman spectra of minerals, it can be easily modified to be used in a more general context, provided a suitable database of Raman spectra is available. [209] Register and co-workers used SERDS for the detection of SERS-encoded gold nanostar probes. They showed the application of SERDS for background removal and signal recovery in spectra of SERS nanoprobes.…”