Temperature-dependent μ-Raman investigation of struvite crystals

• Struvite crystals were grown by single diffusion gel growth technique.
• Raman spectra in range from room temperature to 424 K were recorded.
• The results indicate the phase transition of struvite at 368 K.
• The time-dependent Raman spectra do not indicate structural changes.

The effect of temperature on the vibrational properties of struvite crystals grown from silica gels was systematically studied by μ-Raman spectroscopy. The time-dependent Raman spectra recorded in the process of long time annealing of struvite crystal at 353 K do not indicate structural changes in the struvite crystal with the time of annealing. The temperature-dependent Raman spectra recorded in the range 298–423 K reveal a phase transition in struvite at about 368 K. Above this characteristic temperature, some of bands assigned to vibrations of the PO4 and NH4 tetrahedra and water molecules observed in the Raman spectra in low temperatures (orthorhombic phase) change their spectral parameters or disappear, which indicates a transition to a higher symmetry structure of struvite in the range of high temperatures.

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