High‐pressure Raman spectroscopy of Ca(Mg,Co)Si₂O₆ and Ca(Mg,Co)Ge₂O₆ clinopyroxenes

Abstract

In situ high‐pressure Raman spectra were collected on four pyroxenes, with composition CaCoSi2O6, CaMgSi2O6, CaCoGe2O6 and CaMgGe2O6, up to P = 7.6 and 8.3 GPa for silicates and germanates, respectively. The peak wavenumbers υi increase almost linearly with pressure; the slope dυi/dP is more pronounced for the modes at higher wavenumbers, and higher in germanates than in silicates. No phase transition or change in the compressional behaviour was observed within the investigated P‐range. The strong dependence of the peak position with pressure of the high energy stretching modes is due to the high sensitivity of the vibrational frequencies probed by Raman spectroscopy to subtle changes in the tetrahedral deformation, which are overlooked by single‐crystal X‐ray diffraction. Copyright © 2017 John Wiley & Sons, Ltd.

Low‐temperature sintering of microwave ceramics with high Qf values through LiF addition

“…Therefore, the Raman spectra are almost identical in all samples. According to previous studies, the Raman shift at <300 cm −1 could be attributed to translations of SiO 4 tetrahedron, the peak at 300–450 cm −1 could be assigned to motions of the cations in the M(2) and M(1) sites that were related with tetrahedral chain motion and tilting tetrahedron. Moreover, the Raman shifts in the region of 225‐303, 360, 450‐600, 666, and 1011 cm −1 can be attributed to the O–Li–O bending and Li–O stretching vibrations, the O–Si–O vibrations, the stretching/bending modes of the Si–O–Si bonds, and O–Si–O stretching modes, respectively.…”

Raman spectroscopy, phase transitions, microstructures, and mechano‐luminescence in Ca‐Sr feldspars (CaAl2Si2O8‐SrAl2Si2O8)

“…Moreover, exchange of Ge for Si could have an effect on phase transitions and cation ordering, as previously observed in pyroxenes. 60,61 Finally, the luminescence of feldspars has promising aspects also beyond material sciences. Anorthite can be a host for luminescence activators, even in very small amount.…”

Improved microwave dielectric properties of CaMgSi2O6 ceramics through CuO doping

“…GOpt ¼ 14AgðRÞþ 16BgðRÞþ 13AuðIRÞþ 14BuðIRÞ (6) The theoretical numbers of Raman and IR vibrational modes were 30 and 27, respectively. A strong Raman peak at 1011 cm -1 could be ascribed to the OeSieO stretching modes [24,28,34,35].…”