Mixed transition metal oxides (MTMO) nanoparticles of 3rd-series (NiCo(2)O(4), CuCo(2)O(4), and ZnCo(2)O(4)) were prepared by a co-precipitation method. These were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The particle size was found to be in the order of 53.0, 43.4, and 21.2 nm, respectively. The thermolysis of ammonium perchlorate (AP), AP-HTPB (hydroxyterminated polybutadiene) composite solid propellants (CSPs), and HTPB was found to be catalyzed with MTMOs and the burning rate of CSPs was also enhanced. TG and ignition delay study demonstrated that the higher temperature decomposition (HTD) of AP is catalyzed enormously by these catalysts and CuCo(2)O(4) is the best candidate.