Structural characterization of microwave-synthesized zinc-substituted cobalt ferrite nanoparticles

Microwave combustion technique modified by post treatment procedure is used to synthesize single-phase spinel ferrites of cobalt, zinc, and substituted magnetic nanoparticles of typical size 390 Å. The post treatment does not alter the crystal structure but increases the crystallinity. This is confirmed by powder x-ray diffraction and Fourier Transform Infrared (FTIR) studies. Citric acid is used as a fuel. The fresh synthesized sample shows an impurity phase in x-ray and in FTIR. This is due to the unreacted citrate molecule adsorbed on the particle surface. It is shown that by treating the sample with 0.1 M HCl, we can eliminate the impurity phase, and one can obtain a pure single phase. The magnetization at 8 kOe increases by nearly 8% after the removal of impurity. In order to remove surface adsorbed OH^? ion, samples are treated with NaCl and heated to 200°C for four hours. The XRD result indicates that after the treatment neither the crystallite size nor the distribution changes, but it removes OH^? ion. This is also confirmed by FTIR analysis. Thus, this modified technique can be used to synthesize pure nanocrystalline samples of spinel ferrites.