Raman, infrared and near-infrared spectroscopic characterization of the herderite–hydroxylherderite mineral series

Abstract

Natural single-crystal specimens of the herderite-hydroxylherderite series from Brazil, with general formula CaBePO4(F,OH), were investigated by electron microprobe, Raman, infrared and near-infrared spectroscopies. The minerals occur as secondary products in granitic pegmatites. Herderite and hydroxylherderite minerals show extensive solid solution formation. The Raman spectra of hydroxylherderite are characterized by bands at around 985 and 998 cm(-1), assigned to ν1 symmetric stretching mode of the HOPO3(3-) and PO4(3-) units. Raman bands at around 1085, 1128 and 1138 cm(-1) are attributed to both the HOP and PO antisymmetric stretching vibrations. The set of Raman bands observed at 563, 568, 577, 598, 616 and 633 cm(-1) are assigned to the ν4 out of plane bending modes of the PO4 and H2PO4 units. The OH Raman stretching vibrations of hydroxylherderite were observed ranging from 3626 cm(-1) to 3609 cm(-1). The infrared stretching vibrations of hydroxylherderites were observed between 3606 cm(-1) and 3599 cm(-1). By using a Libowitzky type function, hydrogen bond distances based upon the OH stretching bands were calculated. Characteristic NIR bands at around 6961 and 7054 cm(-1) were assigned to the first overtone of the fundamental, whilst NIR bands at 10,194 and 10,329 cm(-1) are assigned to the second overtone of the fundamental OH stretching vibration. Insight into the structure of the herderite-hydroxylherderite series is assessed by vibrational spectroscopy.

A database of Raman spectra of precious gemstones and minerals used as cut gems obtained using portable sequentially shifted excitation Raman spectrometer

“…Additional medium intensity bands can be found at following wavenumbers: 446, 516, 578, 596, and 1,129 cm −1 . Corresponding bands are located at 998 (ν 1 symmetric stretching vibration of ), 985 ( ), 447 and 516 (ν 2 out of plane vibration of PO 4 and H 2 PO 4 units), 577 and 598 (ν 4 out of plane vibration of PO 4 and H 2 PO 4 units), and 1,128 cm −1 (ν 3 antisymmetric stretching vibration of HOP and PO . No laser‐induced fluorescence was found in the raw spectra.…”

Low-Temperature Crystal Chemistry of Hingganite-(Y), from the Wanni Glacier, Switzerland

“…Unlike isostructural datolite, herderite, and gadolinite [5,25,58,59] the Raman bands of hingganite-(Y) in the 40-1000 cm −1 range have almost similar intensities. The Raman bands at 923 and 983 cm −1 are assigned to stretching vibrations of Si-O in tetrahedral coordination [5,25,58,59]. Be-O stretching vibrations are in the range of 650-800 cm −1 [60].…”

The highly selective oxidation of cyclohexane to cyclohexanone and cyclohexanol over VAlPO4 berlinite by oxygen under atmospheric pressure

“…The spectrum of the VAlPO 4 catalyst exhibited the characteristic vibration absorptions of a berlinite structure [ 5 , 6 , 13 – 16 ], i.e. the bands at 1128 cm −1 are ascribed to the asymmetric Al-O and/or P-O stretching modes and the bands at 804 cm −1 are ascribed to the symmetric Al-O and/or P-O stretch in TO 4 (T = Al or P) [ 5 , 6 , 15 ], the bands at 684 and 458 cm −1 are assigned to the Al-O and/or P-O bending modes [ 5 , 15 , 16 ], and some of which were shifted towards lower wavenumbers probably due to the incorporation of V into the berlinite framework. In addition, a few additional bands at 1089, 747, 684, 653, and 566 cm −1 were also detected in the VAlPO 4 spectrum compared to that for AlPO 4 [ 16 – 18 ].…”