Raman microprobe studies on carbon materials

The Raman spectra of a set of 29 different carbon materials, that included all types of carbonaceous solids of practical interest, were analyzed. The main objectives were to establish whether there is any general tendency where any material can be included, and whether the Raman spectrum (i.e., parameters deduced from it) is sufficient to characterize the degree of structural order in a carbon material. Changes in the spectral profile exhibited the tendencies expected from the graphitization degree of the solids. Deconvolution of Raman spectra allowed separation of the contributions of G, D, D′, and D′′ bands; in addition, a Gaussian band centered at 1330 cm−1, never described before and attributable to impurity ions, was found in the spectra of activated carbons. The width of D band correlates well with the degree of disorder over the entire order-disorder interval, being more adequate than the G-band width as a disorder parameter for disordered materials. Both D- and G-band positions are little useful as measures of disorder, since the former is practically constant whereas the latter varies in a random form. Finally, the graphitization path described by the G′/G band width ratio versus G-band width is evidence of a qualitative difference between the most ordered materials, which become divided into two groups.