<p>Iron oxide is the most common catalyst in solid rocket propellant. We have previously demonstrated increased performance of propellant by encapsulating iron oxide particles within ammonium perchlorate (AP), but only nanoscale particles were used, and encapsulation was only accomplished in fine AP (~20 microns in diameter). In this study, we extended the size of particle inclusions to micron-scale within the AP particles as well the particle sizes of the AP-encapsulated catalyst particles (100s of microns) using fractional crystallization techniques with the AP-encapsulated particles as nucleation sites for precipitation. Here we report catalyst particle inclusions of micron-scale, as well as nanoscale, within AP and present characterization of this encapsulation. Encapsulating micron-sized particles and growing these composite particles could pave the way for numerous possible applications. A study of the thermal degradation of these AP-encapsulated particles compared against a standard mixture of iron oxide and AP showed that AP-encapsulated micron-scale catalyst particles exhibited similar behavior to AP-encapsulated nanoscale particles. Using computed tomography, we found that catalyst particles were dispersed throughout the interior of coarse AP-encapsulated micron-scale catalyst particles and decomposition was induced within these particles around catalyst-rich regions.</p>