Phase transitions of ammonium nitrate doped with alkali nitrates studied with fast X-ray diffraction

Abstract

Dried samples of ammonium nitrate (AN) containing 1, 3, 5 mol% KNO3, RbNO3 and CsNO3 were investigated with temperature resolved X-ray diffraction. The samples were cycled with 2 temperature programs from −70° to 100° and −70° to 150°C, resp. DSC measurements were made for comparison.KNO3 extends the stability range of phase III. The supercooling observed with the transitions II/III and III/IV was so severe that the phases III and IV could be skipped leading to the transitions II/IV and III/V. No hindered nucleation was observed on heating.RbNO3 gives dried AN the properties of the humid nitrate. Phase III appeared on heating but was skipped on cooling, when the sample had been heated to 150°C. Hindered nucleation was observed.CsNO3 stabilizes the phases II and V. No strong hysteresis or supercooling was observed.