[ ] powders were prepared as the oxidation catalyst materials to reduce the emission of particulate matters from diesel engine and their catalytic effects on the oxidation of carbon were investigated. Solution combustion method was employed for the powder synthesis, which uses highly exothermic and selfsustaining reactions. In this study powders were synthesized at as varying the ratio () of fuel (citric acid) and oxidizer (metal nitrate), and their phase and carbon ignition property were examined. As decreases, the crystallinity of synthesized powders enhanced. By calcining at , all the powders synthesized at various fully crystallized. The calcined powders showed carbon ignition temperature as low as , which implied the decrease of the ignition temperature by .