In situ high-temperature Raman and FTIR spectroscopy of the phase transformation of lizardite

Abstract

A temperature-dependent in situ micro-FTIR and micro-Raman spectroscopic investigation was performed on powdered (FTIR, Raman) and single-crystal (Raman) lizardite-1T samples between room temperature and 819 °C. Between room temperature and 665 °C, the OH stretching bands shift to lower wavenumbers, demonstrating a weak expansion of the O3-H3 … O2 interlayer distance. Band deconvolution of FTIR and Raman spectra at room temperature show differences in the number of bands in the OH stretching region with respect to group theory: four (FTIR) and six (Raman) OH stretching bands, respectively. This number reduces to four (Raman) at non-ambient temperatures either caused by LO-TO splitting, the presence of non-structural OH species or the presence of different lizardite polytypes and/or serpentine polymorphs as well as defects. During dehydroxylation, the evolution of the integrated intensity of the OH bands suggests a transport of hydrogen and oxygen as individual ions/molecule or OH -. A significant change in Raman spectra occurs between 639 and 665 °C with most lizardite peaks disappearing contemporaneously with the appearance of forsterite-related features and new, non-forsterite bands at 183, 350, and 670 cm -1 . A further band appears at 1000 cm -1 at 690 °C. The long stability of Si-O-related bands indicates a delayed decomposition of the tetrahedral sheet with respect to the dehydroxylation of the octahedral sheet. Moreover, evidence for a small change in the ditrigonal distortion angle during heating is given. In general, all appearing non-forsterite-related frequencies are similar to Raman data of talc and this indicates the presence of a talc-like intermediate.

Fe-bearing phases in modern lacustrine microbialites from Mexico

“…6b; Wilkins and Ito, 1967). Again, these bands are significantly different from those observed in 1:1 layered configuration silicates such as serpentines, which appear at 3652, 3669, 3688 and 3703 cm -1 for lizardite (Trittschack et al, 2012) or 3644 and 3689 cm -1 in chrysotile (Bishop et al, 2002). Last but not least, the ν 3 CO 3 band at 1384-1385 cm -1 was detected in La Preciosa, Atexcac, La Alberca de Los…”

Submicron Raman spectroscopy mapping of serpentinite fault rocks

“…However, the peaks in lizardite and chrysotile have an identical shape, overlap with other silicate minerals, and their positions tend to shift as shown by the variations reported in the literature (Figure S2). Antigorite also has a weak, unique peak at 1,045 cm −1 , but this has little utility in high‐throughput mapping …”

“…The spectra and dominant peaks shown in Figure 2 are consistent with published literature wavenumber values ( Figure S2). [12,13,34,35,38,[44][45][46][47][48] The hydroxyl peak positions may vary by ±2 wavenumbers between samples-this is likely due to local cation substitutions. [12,13,22,34,[48][49][50] These low levels of substitution do not manifest as additional bands but cause minor distortions in the crystal lattice and slightly alter the energetics of vibrational modes.…”

“…However, the peaks in lizardite and chrysotile have an identical shape, overlap with other silicate minerals, and their positions tend to shift as shown by the variations reported in the literature ( Figure S2). [12,13,34,35,38,[44][45][46][47] Antigorite also has a weak, unique peak at 1,045 cm −1 , but this has little utility in highthroughput mapping. [12] The high-wavenumber region, corresponding to O-H stretching vibrations, has been shown to allow for definitive identification of the main serpentine minerals due to the different band shapes.…”

Infrared Spectroscopic Study of Vibrational Modes across the Orthorhombic–Tetragonal Phase Transition in Methylammonium Lead Halide Single Crystals

“…The thermocouple was calibrated using melting points of different salts (melting points between 580 K and 1074 K) as described elsewhere. 50 The 0°C point (freezing of H 2 O) was included in the calibration line. Based on the phase transition temperature of MAPbI 3 T t = 161 K (Tab.…”