Raman-Infrared (IR) Spectroscopy Study of Natural Cordierites from Kalahandi, Odisha

Abstract

A combined Raman and IR spectroscopic study has been carried out on natural cordierite samples from Kalahandi district, Odisha to understand the effect of Mg-Fe2+ exchange on Raman peak shift and to identify the volatile species within these cordierite crystals. In the field, the cordierites are hosted by silica-saturated quartz-feldspathic rocks, mafic granulites and also by the silica-undersaturated Mg-Al granulites. X-ray Diffraction (XRD), Raman spectroscopy and microprobe analyses were initially used to characterize the samples and to obtain chemical composition respectively. XRD of the gem quality cordierite reveals perfect orthorhombic symmetry, supported by Raman analyses that deduce the extent of Al-Si ordering in this mineral. Microprobe data indicate that most cordierites are Mg-rich (XMg = 0.93-0.94), however, a variation in Mg/Fe concentration of cordierite from different locations is observed. The samples also show high Na content that are associated with quartzo-feldspathic rocks intruded by pegmatites, than that of the Mg-Al granulites. This result suggests temperature variance in cordierite crystallization among different host rocks. Raman spectra of these cordierites define structurally resolved Raman vibrational modes where the magnitude of peak shift of most bands towards lower wavenumber than pure Mg-cordierite is proportional with Fe concentration, and are linked with the extent of Mg-Fe exchange within cordierite structure. FTIR study confirms the presence of both type-I and type-II waters along with significant amount CO2 as channel constituents, however, type-I H2O and CO2 concentrations vary within a single crystal. The FTIR spectroscopic evidence strongly supports a H2O and CO2 bearing fluid composition during crystallization of cordierite from these localities.

Characteristics of Cordierite (Iolite) of Bandarguha-Orabahala Area, Kalahandi District, Odisha, India

“…Biotite, orthopyroxene, sillimanite, corundum, feldspars and quartz have been identified in the cordierite samples which corroborate the observations of [2,3,10]. One of the possible reactions for cordierite formation is: orthopyroxene+sil limanite+quartz=cordierite+K-feldspar+water.…”

“…A part of iron in the cordierite structure is possibly present in the form of Fe 3+ that facilitate charge transfer process resulting in blue to violet pleochroism, hence, rendering these stones as gem quality cordierite (iolite) [10].…”

Structure, crystallization, and performances of alkaline‐earth boroaluminosilicate sealing glasses for SOFCs

“…It is seen that the intensity of the peak at ~530 cm −1 decreases gradually with extending the heat‐treatment duration, whereas the peak at ~680 cm −1 (i.e., vibration of Q 1 ) is enhanced and the peak position at 987 cm −1 shifts to a higher wavenumber (about 1013 cm −1 ). The phase marked by Area 3 in Figure 4B might be the cordierite (Mg 2 Al 4 Si 5 O 18 ) phase 21,22 . In the maps of Figure 4C,D, it can be observed that CG and SG are phase‐separated when heat‐treated for 4 h. The peak at ~1000 cm −1 (mixed Q 2 and Q 3 ) shifts to a higher wavenumber (Areas 2‐5) compared to the spectra of the as‐quenched samples (CG and SG).…”

Caracterização tecnológica de catalisadores automotivos desativados visando o aproveitamento de Pt, Pd e Rh

“…O espectro Raman do catalisador automotivo pode ser visto na Figura 3. A base literária de espectros Raman de catalisadores automotivos é muito limitada, logo, a análise dos espectros foram baseadas em literaturas dos componentes isolados [14,15].…”

“…Os picos que mais se destacam na Figura 3 são de cordierita, representados pelo símbolo (α), esses resultados estão de acordo com os trabalhos de Likhacheva et al [14] e Majumdar e Mathew [15], que estudaram a cordierita de maneira mais ampla. Os dois picos a 973 e 1185 cm -1 podem ser atribuídos às vibrações internas de alongamento de SiO 4 da estrutura de cordierita [16].…”