Inexpensive light-metal amides are among the most highly active and effective ammonia decomposition catalysts at modest temperatures and are likely to surpass the performance of optimised transition metal based catalysts. Creating mixed metal amide systems is one way to tailor their function as catalysts. In-situ, combined powder diffraction and gravimetric studies on the formation and decomposition of two such materials, Na2Mg(NH2)4 and K2Mg(NH2)4 will be carried out. As the first non Li-containing mixed metal amide NH3 decomposition catalysts to show high post reaction mass recovery, understanding their complex reaction mechanisms will be a crucial step in the further development of amide-based catalysts. These systems are structurally under-explored, but chemically important as they are known to form novel mixed amide-imide complexes at high temperatures.