Rare-earth styphnates: feasible alternatives for lead styphnate?

Abstract. Significant research is being conducted into finding alternatives for the lead-containing primary explosive lead styphnate (LS), and while valuable alternatives have been found, LS is still used in most commercial and military primers, as well as in electric initiators and impulse cartridges. Whereas its key benefits lie in its reliable ignition capability, its cost-effectiveness and its widespread application, the fact that it contains lead makes it a toxic and hazardous substance, justifying the research efforts towards more sustainable alternatives. Rare-earth (RE) coordination chemistry is the study of coordination compounds involving rare-earth elements (REE) as the central metal ions, with their unique electronic, magnetic and optical properties. Even though many of the REE are considered to be critical elements, due to the balance problem, some of them are mined in excess of their demand, and could be viable sources for novel energetic materials. In this study, we synthesized the styphnate salts of all REE, except for Sc and the radioactive Pm. Preliminary tests indicate that the RE styphnates form as pure compounds with properties of primary explosives, exhibiting decomposition temperatures around 300°C, but with a significantly lower sensitivity to electrostatic discharge than LS.