Raman Study of Barite and Celestine at Various Temperatures

Abstract

The Raman spectra of barite and celestine were recorded from 25 to 600 °C at ambient pressure and both minerals were stable over the entire temperature range. Most of the Raman bands of barite decreased in wavenumber with increasing temperature with the exception of the ν2 modes and the ν4 band at 616 cm−1, which did not exhibit a significant temperature dependence. These vibrations may be constrained by the lower thermal expansion along the a-axis and b-axis of barite. Similar to barite, most of the Raman bands of celestine also decreased in wavenumber with increasing temperature, with the exception of the ν2 modes and the ν4 band at 622 cm−1, which showed very little variation with increasing temperature. Variations of Raman shift as a function of temperature and FWHM (full width at half maximum) as a function of Raman shift for the main, ν1 modes of barite and celestine show that both minerals have almost identical linear trends with a slope of −0.02 cm−1/°C and −0.5, respectively, which allows for the prediction of Raman shifts and FWHM up to much higher temperatures. The calculated isobaric and isothermal mode Grüneisen parameters and the anharmonicity parameters show that the M–O modes (M = Ba2+ and Sr2+) in barite and celestine exhibit much higher values of both mode Grüneisen parameters and anharmonicity than the SO4 tetrahedra. This indicates that the S–O distances and S–O–S angles are less sensitive to pressure and temperature increase than the M–O distances in the structure. Furthermore, the generally higher anharmonicity in celestine is due to the smaller size of the Sr2+ cation, which causes the celestine structure to be more distorted than the barite structure.

Equilibrium barium isotope fractionation between minerals and aqueous solution from first-principles calculations

“…11, Persson et al (1995). Experimental data: Raman spectra for witherite and barite (Zhou et al, 2020); Infrared spectra for witherite (Chaney et al, 2015; and barite (Dimova et al, 2006;Lane, 2007).…”

Raman imaging of Micrasterias: new insights into shape formation

“…With bands at 986 cm −1 , 615 cm −1 , and 452 cm −1 (Fig. 1b, black line), it was assigned to barite (BaSO 4 ), as exactly these three bands are reported as the strongest in BaSO 4 (Zhou et al 2020). The corresponding distribution maps showed that two of the carbohydrate spectra refer to the cell wall (red, pink) and one to the cell content (green) (Fig.…”

Editorial for the Special Issue “Modern Raman Spectroscopy of Minerals”

“…At least in parts of six out of seven studies published in this Special Issue, Raman micro-spectroscopy instruments according to the principle shown in Figure 1b were used [5][6][7][8][9][10]. Although only N. Böhme et al made use of the full imaging capabilities of such instruments [9], some groups employed Raman microscopes for performing in situ measurements in heating stages developed for microscopic observation [7][8][9], and others needed the spatial resolution for specifically choosing spots for single-point measurements within complex samples [6], including positioning in three-dimensional space for identifying mineral inclusions [10]. These possibilities demonstrate why microspectroscopy instruments have become relatively widespread in research laboratories specialising in Raman spectroscopy.…”

“…The potential of SHS for mobile Raman spectroscopy was recently underlined by the presentation of a monolithic device of about 35 mm linear dimension and less than 100 g weight by the group of S. M. Angel et al [13]. The studies by L. Zhou et al [8], T. Schmid et al [7], and N. Böhme et al [9] make use of the in situ measurement capabilities of Raman spectroscopy by employing heating stages developed for microscopic observation. While all three studies derive characteristics of thermal expansion or phase conversions from single-spot temperature-and/or time-resolved measurements of minerals, N. Böhme et al additionally realised in situ Raman microspectroscopic imaging by fast mapping during sample heating [9].…”

“…This Special Issue includes technological developments and applications in the field of modern Raman spectroscopy of minerals in a broad sense, from natural mineral deposits and archaeological objects to inorganic phases in man-made materials. The studied minerals include fossil resins [4], typical rock-forming minerals (calcite, quartz, forsterite) [5], iron-sulphur species (e.g., mackinawite) [6], a range of sulphates (gypsum, bassanite, anhydrite III, anhydrite II [7]; celestine, barite [8]; ternesite [9]), as well as silicate minerals like garnets (e.g., almandine) [10].…”