The decomposition of silver azide

Abstract

The thermal decomposition of both allotropic forms of silver azide as polycrystalline material and as single crystals has been investigated. The activation energies are 44 to 46 kcal/mole (low-temperature form) and 31 to 32 kcal/mole (high-temperature form). The spectra of freshly prepared and of partially decomposed crystals have been examined and various colour centres tentatively identified. Measurements of the ionic and electronic conductance of unsintered and sintered polycrystalline material together with those of thermo-electric power lead to the conclusion that the charge carriers are interstitial silver ions and electrons. From results of the photoconductance response at various wavelengths, the width of the zone for intrinsic conductance in pure silver azide has been evaluated, and also the optical activation energies in partially decomposed salt for electron excitation from colloidal centres to the conduction band for both allotropes. The temperature coefficients of electronic conductance in partially decomposed material in the quenched and in the annealed state have also been measured, and allow an evaluation of the corresponding thermal activation energies, and hence of the ratios of the static and high-frequency dielectric constants. A possible rate-determining step in the thermal decomposition has, in consequence, been suggested and a tentative theory of the subsequent processes proposed.