Infrared Spectroscopy Investigation of Ammonium Sulfate at Low Temperatures

We present a comprehensive study of ammonium sulfate between 30 and 300K us-
ing Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry
(DSC) and neutron powder diffraction (NPD) to investigate the paraelectric to ferro-
electric phase transition. Heat capacity measurements taken with DSC show a clear
anomaly at the phase transition (223 K). This phase transition in ammonium sulfate
is associated with temperature dependent hydrogen bonding and presents an interest-
ing and challenging research area.¹ We characterize the hydrogen bonds at different-
temperatures and compare our NPD at room temperature with previously reported
results². We then analyze FTIR spectral features of the sample and demonstrate their
temperature dependent displacement.

[1] Malec, L. M., Gryl, M., & Stadnicka, K. M., Inorg. Chemistry, 57, 4340–4351
(2018).
[2] E. O. Schlemper and W. C. Hamilton, J. Chem. Phys. 44, 4498 (1966)