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Struvite (MgNHPO·6HO) was heated to temperatures from 55 to 300 °C. X-ray diffraction analysis revealed struvite was stable at 55 °C, partially decomposed to dittmarite (MgNHPO·HO) at 100-200 °C, and formed an amorphous phase at 250-300 °C. Thermogravimetric analysis confirmed sample mass loss consistent with dittmarite formation at 100-200 °C and evolution of all volatiles at 250-300 °C. Fourier transform infrared (FTIR) spectroscopy detected the ν NH band in 55-200 °C solids, as expected for struvite and dittmarite. This band decreased in intensity at 250 °C, and was not evident at 300 °C, confirming loss of NH(s) at these temperatures. FTIR spectra also showed changes in the vibrations of the ν PO band. At 55 °C, splitting in the band indicated destabilization of the PO(s) group despite no change in mineralogy. Vibrations at 100-200 °C were associated with dittmarite and MgHPO, and at 250-300 °C, MgHPO and MgPO. Analysis of acid-digested solids indicated the presence of P other than P-PO at 200-250 °C, confirming MgPO formation. Overall, heat treatment of struvite produces several decomposition products, complete identification of which requires the use of multiple approaches. Temperature-induced phase transformations along with emission of NH(g) have implications for use of struvite in multiple applications. [ABSTRACT FROM AUTHOR]