A vibrational spectroscopic study of the phosphate mineral vantasselite Al4(PO4)3(OH)3·9H2O

Abstract

We have studied the phosphate mineral vantasselite Al₄(PO₄)₃(OH)₃·9H₂O using a combination of SEM with EDX and Raman and infrared spectroscopy. Qualitative chemical analysis shows Al, Fe and P. Raman bands at 1013 and 1027 cm(-1) are assigned to the PO₄(3-)ν₁ symmetric stretching mode. The observation of two bands suggests the non-equivalence of the phosphate units in the vantasselite structure. Raman bands at 1051, 1076 and 1090 cm(-1) are attributed to the PO₄(3-)ν₃ antisymmetric stretching vibration. A comparison is made with the spectroscopy of wardite. Strong infrared bands at 1044, 1078, 1092, 1112, 1133, 1180 and 1210 cm(-1) are attributed to the PO₄(3-)ν₃ antisymmetric stretching mode. Some of these bands may be due to δAl₂OH deformation modes. Vibrational spectroscopy offers a mechanism for the study of the molecular structure of vantasselite.

Acid-based geopolymers: Understanding of the structural evolutions during consolidation and after thermal treatments

“…At 110°C, additional bands appear at 1230, 1180 cm -1 ( P-O) , 730 and 715 cm -1 ( Al-O) attributed to AlPO 4 with tridymite-and cristobalite-like structures [20,21]. Moreover, the contribution located at 1130 cm -1 can be assigned to the  P-O of all AlPO 4 polymorphs [20,22]. In the temperature range 110°C-200°C, bands at 1114 cm Moreover, those data prove the existence of aluminophosphate nuclei, which is in agreement with the previous study of the geopolymer consolidation.…”

“…The 1800 to 600 cm -1 parts of the spectra are presented in Figure 7B. At room temperature, contributions at 1220 (w), 1155 (w), 1095 and 920 cm -1 are typical of stretching P-O bands of hydrated aluminophosphate [22,27]. The bands corresponding to Si-O-Si species (Q 4 , Q 3 , Q 2 , Q 1 ) are overlapped by the P-O contributions and only the bending of Si-O-Si is detected at 800 cm -1 .…”

“…It is also a refractory phase isostructural with silica with many polymorphs, the most common ones being berlinite (hexagonal), cristobalite (triclinic, hexagonal) and tridymite (orthorhombic, cubic) [ 16 ]. Those main polymorphs can be differentiated by X-Ray Diffraction (XRD) [17,18,19], Fourier-Transform Infrared (FTIR) [20,21,22] and Nuclear Magnetic Resonance (NMR) [23,24,25] spectroscopies. Finally, AlPO 4 also exists in various hydrated AlPO 4 .xH 2 O phases which can be characterized by XRD [26,27] and FTIR spectroscopy [22,27] as well.…”

Control of the alumino-silico-phosphate geopolymers properties and structures by the phosphorus concentration

“…More specifically, the bands located at 3680, 3570, 3440, 3350 and 3240 cm -1 are respectively attributed to the following bonds: P-OH, SiOH (asym and sym), OH -AlPO4 and bonded H2O[11,22,23]. The contributions around 1640 cm -1 are assigned to the bending of P-OH and water molecules, those at 1220 (w), 1155 (w), 1095 and 920 cm -1 to the stretching of P-O from hydrated aluminophosphates[24,25], and the one at 800 cm -1 is related to the bending of Si-O-Si bonds. The bands in the range 1300-500 cm -1 do not evolve significantly with the addition of water and their identification remains complex due to the presence of silicate species in the same region.…”

Crystal Structure, Raman Spectroscopy and Dielectric Properties of New Semiorganic Crystals Based on 2-Methylbenzimidazole

“…The lines at 1637 cm −1 and 1515 cm −1 (Nos. 5 and 8), observed in three new crystals, probably correspond to oscillations inside the water molecule [48][49][50]. Figure 9 demonstrates the polarized Raman spectra of the MBI-phosphite crystal (recorded by T64000 Advanced Research Raman System) in different experimental geometries.…”