Vibrational spectroscopic characterization of the phosphate mineral phosphophyllite – Zn2Fe(PO4)2·4H2O, from Hagendorf Süd, Germany and in comparison with other zinc phosphates

This research was undertaken on phosphophyllite sample from the Hagendorf Süd pegmatite, Bavaria, Germany. Chemical analysis was carried out by Scanning Electron Microscope in the EDS mode and indicates a zinc and iron phosphate with partial substitution of manganese, which partially replaced iron. The calculated chemical formula of the studied sample was determined to be: Zn2(Fe0.65, Mn0.35)∑1.00(PO4)2·4(H2O). The intense Raman peak at 995 cm−1 is assigned to the ν1 PO 4 3 - symmetric stretching mode and the two Raman bands at 1073 and 1135 cm−1 to the ν3 PO 4 3 - antisymmetric stretching modes. The ν4 PO 4 3 - bending modes are observed at 505, 571, 592 and 653 cm−1 and the ν2 PO 4 3 - bending mode at 415 cm−1. The sharp Raman band at 3567 cm−1 attributed to the stretching vibration of OH units brings into question the actual formula of phosphophyllite. Vibrational spectroscopy enables an assessment of the molecular structure of phosphophyllite to be assessed.