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The interest in 3d-series metal oxides has increased in the last decades. Among the transition metal oxides, nickel oxide (II) received a lot of attention due to its various applications in several technological fields. Nickel oxide (II) is a p-type semiconductor because it has structural defects that can be caused by vacancy of Ni ions [1]. Another important oxide is the nickel manganite, which is a ferrimagnet and its main application is as a negative temperature coefficient (NTC) thermistor [2]. Crystalline powders of nickel oxide (NiO) and nickel manganite (NiMn2O4) were synthesized by new and simple chemical route which is based on the use of sorbitol as a chelating agent. The samples obtained were analyzed by X-ray powder diffraction and scanning electron microscopy (SEM) as a function of firing temperature, heating rate and firing time. The average crystallite size (D) was obtained by Scherrer’s equation. Results analysis confirm one single phase of cubic NiO at 500 °C and cubic spinel NiMn2O4 at 800 °C. The SEM micrograph shows the formation of agglomerates comprising particles. Different heating rate produced very different particle sizes. According to our result the best heating rate for the production of single phase of NiO and NiMn2O4 is 10 °C/min.