FTIR, XRF and Powder XRD Experimental Study of Charoite: Crystal Chemical Features of Two Associated Generations

Канева, Е. В.; Radomskaya, T. A.; Shendrik, R. Yu.; Чубаров, В. М.; Amosova, Alena A.; Mitichkin, M. A.

doi:10.1007/978-3-030-49468-1_13

Cited by 4 publications

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“…Naturally occurring aggregates of chain silicate crystals and their synthesized analogs are well known in the production of bioactive ceramics for their strength and fracture resistance. The structural features of the minerals of this group of rare alkaline Ca-(K)-(Na) silicates make these materials promising for ion exchange, since, as noted in [6][7][8][9][10][11][12][13][14][15][16]18,19], the crystal structures contain several cationic positions suitable for doping with transition metals and lanthanides. Finally, materials activated with transition and rare earth elements are widely used in various fields of photonics.…”

Section: Introductionmentioning

confidence: 99%

Tinaksite and Tokkoite: X-ray Powder Diffraction, Optical, and Vibrational Properties

Канева

Shendrik

2022

Crystals

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In this study, natural tinaksite (K2Ca2NaTi[Si7O18OH]O) and tokkoite (K2Ca4[Si7O18OH](OH,F)) collected in charoite rocks of the Murun alkaline massif (Siberia, Russia) were examined by X-ray diffraction and optical and vibrational spectroscopic methods. A comparative analysis of the experimental diffraction patterns with respect to the calculated X-ray powder diffraction patterns was carried out for tinaksite and tokkoite powders. The shift in the diffraction peaks of tinaksite is explained by the smaller values of the unit cell parameters a and b as compared with those of tokkoite. A similar shift of the peaks is also observed in the Raman and infrared absorption spectra; however, this feature is explained by the difference in the chemical composition of the minerals. The shoulder in the absorption spectra at about 800 nm in tinaksite and 700 nm in tokkoite corresponds to the presence of Mn2+ and Fe3+ absorption bands, the presence of which determines the color of tinaksite and tokkoite. The luminescence band with a maximum at about 540–550 nm in the photoluminescence spectra is related to Mn2+ centers, while an additional band at about 610 nm can be associated with Ti3+ centers in tinaksite. The intensity of the Fe3+ ESR signal increases in both samples after heating, while the intensities of the bands associated with OH groups decrease in tinaksite and tokkoite. This characteristic is the result of iron oxidation and dehydrogenation reaction.

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