A mixture of Fe and KClO4 (84/16, wt/wt) was studied as an iron heat-powder. The combustion products were Fe, FeO, and KCl, which show semiconductor properties, with a conductivity on the order of 10(3) S cm(-1). Based on energy-dispersive X-ray analysis (EDX) of samples from characterization tests, a core-shell structure of combustion products was discovered, where the core consisted of unreacted Fe and the shell of FeO. Transmission electron microscopy (TEM) images of the combustion products confirmed the thickness of the shell (similar to 0.2 mu m), consistent with the calculated value. VC 2011 The Electrochemical Society. [DOI: 10.1149/1.3599422] All rights reserved.