One of the methods of thermodynamic stabilization of AN (ammonium nitrate) crystals, which is currently used not only as nitrogen fertilizer, but also as an environmentally friendly oxidant for gas-generating fuels for various purposes, is the technology of obtaining low-defect crystal structures. It is known that the potassium ion is a phase stabilizer of AN, and chlorine-containing compounds affect the rate of thermal decomposition of AN; therefore, there has been made an attempt to use a modifier, which includes both elements: potassium salt of monochloroacetic acid (PMCHAA) and to study its effect on phase transitions and thermal decomposition of AN depending on the amount of additive, type of solvent and crystallization temperature. As a result of the tests, it has been found out that a sample containing 1% PMCHAA (obtained at 80 ° C from an aqueous medium) most fully meets the requirements for EnCS oxidizers: the rate of thermal decomposition of the sample is 2.65 times higher than that of AN crystals recrystallized under the same conditions; the rate of modification transition IV – III has been reduced by almost 3 times

Keywords: ammonium nitrate, oxidizer, gas-generating compositions, polymorphic transition, thermal decomposition, additive, kinetics, thermodynamics, potassium salt of monochloroacetic acid, solvent, co-crystallization