The thermal decomposition of 5-aminotetrazolium nitrate (5-ATZN) was studied at a heating rate of 10degreesC/min from 50 to 600degreesC/min by DSC and TG techniques. Two intense exothermic processes are observed and the solid decomposition residues were thermally stable cyclic azines. Crystals of 5-ATZN were obtained from the aqueous solution by slow evaporation at room temperature. They crystallize in the monoclinic space group P2(1)/c with crystal parameters: a = 1.0606(2) nm, b = 0.35065(4) nm, c = 1.4641(2) nm, beta = 90.63(1)degrees, V = 0.5444(1) nm(3), 7 = 4, D-c = 1.807 g/cm(3), mu(MoKalpha.) = 0.168 mm(-1), F(000) = 304. The structure consists of NO3- anions and [5-ATZH](+) cations, of which the 4-N was protonized. Electrostatic interaction and intermolecular hydrogen bonds assemble the ions into 2D layered structures. (C) 2004 Elsevier B.V. All rights reserved.