Structure and stability of inorganic azides. II. Some physical and optical properties, and the fast decomposition of solid monovalent inorganic azides

Abstract

The stability (isothermal decomposition) to heat and light of a series of monovalent inorganic azides is considered. The stability decreases in the order KN3, TIN3, AgN3and CuN3. This is the order of increasing ionization potential of the metal. Measurements have been made on a number of the physical properties of these compounds, such as the refractive indices, ab­sorption spectra, photoconductivity, and melting points. The electron energy levels of these solids has also been estimated. These include the energy (optical and thermal) required to form an exciton and where appropriate the energy required to dissociate the exciton to give an electron in the conduction band. The relation of these measurements to the decomposition mechanism is considered. The critical light energy required to ignite a pellet of silver azide is reduced by the addition of colloidal gold (or silver). The metal particles are thought to act as electron traps during the initial photochemical decomposition. This increases the extent of the decomposition. The growth of the explosion, however, is a thermal process in which there is self heating of the azide and an accelerated rate of decomposition. A molten phase is probably necessary for the fast decomposition of the inorganic azides.