The effect of ferric and manganese oxide dopants on thermal and physicochemical properties of Mn-oxides/Al2O3 and Fe2O3/Al2O3 systems has been studied separately. The pure and doped mixed solids were prepared by impregnation method, then thermally treated at (400-1000 degreesC). Pyrolysis of pure and doped mixed solids was investigated via thermal analysis (thermogravimetry (TG) and differential thermogravimetry (DTG)) techniques. The thermal products were characterized by means of X-ray diffraction (XRD) analysis. The catalytic behavior of the thermal products was tested using the decomposition of H2O2 reaction. The results revealed that pure ferric nitrate decomposes into Fe2O3 at 350 degreesC and shows thermal stability up to 1000 degreesC. Pure manganese nitrate yields MnO2 at 300 degreesC and Mn2O3 at 500 degreesC and Mn3O4 at 1000 degreesC. Crystalline gamma-Al2O3 phase was detected for all samples preheated up to 800 degreesC. Ferric and manganese oxides enhanced the crystallization of alpha-Al2O3 phase at 1000 degreesC. Each of ferric, manganese, and aluminum oxides have thermal effect on the thermal decomposition products of the mixed components. Crystalline MnAl2O4 and MnFe2O4 phases were formed at 1000 degreesC as a result of solid-solid interactions between the corresponding thermal products. Fe2O3 doping increased the catalytic activity of Mn2O3/Al2O3 system up to certain limit, and has an inhibiting effect by increasing its content above this limit. The catalytic activity of Fe2O3/Al2O3 system progressively increased with increasing the manganese oxide dopant.