Frankamenite: Relationship between the Crystal–Chemical and Vibrational Properties

Abstract

The study provides novel insights into the crystal–chemical and optical characteristics of frankamenite. Frankamenite belongs to a special group (canasite group) of the complex alkaline Ca-(K)-(Na) silicates, and it was found in charoitites from the only known location, Murun Massif, Eastern Siberia, Russia. The crystal–chemical, vibrational, and optical properties of frankamenite were investigated by combining electron probe microanalysis (EPMA), single-crystal X-ray diffraction (SCXRD), infrared (IR) absorption, Raman, UV-Visible absorption, and electron spin resonance (ESR) spectroscopy. The behavior of the peaks in the IR spectra was also studied using ab initio calculations. Detailed characteristics of the internal composition and structure of the mineral species were described, and vibrational and optical properties based on these peculiarities were interpreted. The thermally stimulated reorientation of the H2O molecules and OH− groups was studied by thermo-Raman spectroscopy. Octahedral cationic positions can be readily doped with transition metal and lanthanide ions that provide a promising opportunity to adjust the Ce3+ luminescence. Hence, frankamenite is a potential material for ion exchange, novel phosphors, and luminophores.

An Apatite-Group Praseodymium Carbonate Fluoroxybritholite: Hydrothermal Synthesis, Crystal Structure, and Implications for Natural and Synthetic Britholites

“… 84 On the other hand, the position of the Ce 3+ luminescence band can be estimated to be around 410 nm based on the mean M 2–O distance. 85 Therefore, we infer that the observed luminescence bands at 305 and 325 nm are attributed to 5d–4f transitions in Pr 3+ ions.…”

“…The presence of carbonate adjacent to Pr 3+ cations, for the same reason, can cause an even greater shift of the band toward lower energies . On the other hand, the position of the Ce 3+ luminescence band can be estimated to be around 410 nm based on the mean M 2–O distance . Therefore, we infer that the observed luminescence bands at 305 and 325 nm are attributed to 5d–4f transitions in Pr 3+ ions.…”

Co-Doping Effect of Mn2+ and Eu3+ on Luminescence in Strontiowhitlockite Phosphors

“…The absorption bands of Mn 2+ are typically found in the 370–440 nm spectral range and are attributed to d-d transitions. These absorption bands often have a low oscillator strength and can appear broadened when Mn 2+ ions occupy multiple non-equivalent positions within the lattice [ 46 , 47 ]. Additionally, a prominent absorption edge is observed in this region.…”