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In the present context, ammonium sulfate (NH4)2SO4 crystal phase stability has been examined at shocked conditions and observed that the title crystal undergoes the reversible crystallographic phase transitions with respect to the number of shock pulses and the observed phase transition sequence is Pnam-Pnam-distorted Pnam- Pnam-Pnam for 0,1,2,3, and 4 shocks, respectively and the observed phase transition sequence is evaluated by X-ray diffraction (XRD), Raman spectroscopy and optical spectroscopy (UV-DRS). Based on the observed analytical experimental results, it is authenticated the occurrence of the reversible phase transition which is caused by the molecular distortions accompanied by the rotational disorder of ammonium and sulfate groups of ions because of the impact of shock waves. This report is the first of its kind regarding the switchable phase transition inclusive of static temperature experiments observed for title crystal.

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Exploration of the structural stability of the single and poly‐crystalline materials of solid‐state at high temperature and pressure is one of the basic research topics in the materials science branch. While the initial state of material undergoes change because of external factors, the functional properties of the material are usually significantly varied and hence, detailed investigations are highly required to better understand either change in properties or stability of materials with respect to their initial states. En route to this process, the crystallographic phase stability of sodium nitrate poly‐crystalline samples are studied at dynamic shocked conditions and the observed results are compared to the previously reported sodium nitrate single crystal. The structural stability profile of the test sample is assessed by X‐ray diffraction, Raman spectroscopic and optical spectroscopic techniques. Surface morphology features are obtained from the scanning electron microscopic (SEM) technique. The overall observation of the diffraction, spectroscopic and morphological analyses shows that the poly‐crystalline sodium nitrate sample has higher stability than that of the single crystal of sodium nitrate. The detailed interpretations are presented in the following sections.