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RESEARCH PRODUCT

Differential scanning calorimetric and Raman studies of phase transition V ⇌ IV of ammonium nitrate

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Abstract Differential scanning calorimetry, alone and in conjunction with Raman spectrophotometry for simultaneous calorimetric and spectral measurements, was used to study the solid state phase transitions of ammonium nitrate between − 50 and 100 °C. On heating, two transition paths were observed between − 40 and 0 °C: one showing two separate peaks in DSC and the other showing a single peak. The latter path became dominant when samples were thermally cycled. The double transition was followed by transition IV →II at 51 °C and the single transition by transitions IV → III → II at about 50 and 87 °C. Raman spectra showed that there were two phases present between the two DSC peaks at low temperature. The first peak was attributed to a transition from the phase here designated as V to phase IV, and the second peak to a transition from V to IV. The single peak under 0 °C was the transition V → IV.