Thermal decomposition of potassium tetrahydridoaluminate as probed by Al-27 and K-39 NMR

Polycrystal line samples of potassium tetrahydridoaluminate KAlH4 subjected to various degrees of thermolysis were studied by Al-27 and K-39 NMR. The contents of solid products and their compositions were determined. The majo r products of decomposition are aluminum metal, potassium hydride KH, and p otassium hexahydridoaluminate K3AlH6. The concentration of K3AlH6 nonlinear ly depends on the degree of thermolysis and is roughly two times lower than the value that follows from the reaction of decomposition. Possible reason s for this difference are discussed.