Combustion method has been used as a fast and facile method to prepare nanocrystalline Co3O4 spinel employing sucrose as a combustion fuel. The products were characterized by thermal analyses (TGA and DTA), X-ray diffraction technique (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. Experimental results revealed that the molar ratio of fuel/oxidizer (F/O) plays an important role in controlling the crystallite size of Co3O4 nanoparticles. Transmission electron microscopy indicated that the crystallite size of Co3O4 nanocrystals was in the range of 13–32？nm. X-ray diffraction confirmed the formation of CoO phase with spinel Co3O4. The effect of calcination temperature on crystallite size and morphology has been, also, discussed. 1. Introduction Spinel cobalt oxide (Co3O4), an important antiferromagnetic -type semiconductor, is a technologically important and functional material, owing to its unique structure, intriguing properties, and potential practical applications in several important technological fields such as heterogeneous catalysis [1], solid state sensors [2], electrochromic sensors [3], anode materials in Li ion rechargeable batteries [4], energy storage [5], pigments and [6]. It is well known that the morphology and size of Co3O4 have a great influence on its properties, which are thus a key factor to their ultimate performance and applications. In this regard, it is desirable to tailor-synthesize nanoparticles with predesigned morphology and size distributions. Co3O4 with nanosized high surface area is expected to lead to even more attractive applications in conjunction of their traditional arena and nanotechnology [7]. Therefore, it is important to prepare Co3O4 with defined morphologies and a narrow range of size distribution. Much effort has been made to synthesize nanocrystalline Co3O4, with various particle sizes, from economical and practical aspects point of view including thermal decomposition of cobalt oxalate (60–200？nm) [8], one-pot hydrothermal reaction (average size 30？nm) [9], thermal decomposition of sol-gel derived oxalates (15–20？nm) [10], and solution combustion method (23–90？nm) [11]. Focusing our attention to the combustion route, it involves a self-sustained reaction between an oxidizer (e.g., metal nitrate) and a fuel (e.g., urea, sucrose, glycine, and hydrazides). This process not only yields nanosize oxide materials, but also allows uniform (homogeneous) doping of trace amounts of rare-earth impurity ions in a single step.
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