Nanopowders of two different compositions of cerium gadolinium oxides designated as CGO1 (Ce0.9Gd0.1O2) and CGO2 (Ce0.8Gd0.2O1.9) have been synthesized by a sodium alginate (Na-ALG) mediated novel ion-exchange process. The results indicate that the nanopowders having a final particle size of similar to 7 nm can be obtained after calcination of ion-exchanged alginate precursor at 500 degrees C for 2 h in ambient air. The chemical structures of Na-ALG solution and CGO beads are analyzed by Fourier transform infrared spectroscopy (FTIR). X-ray diffraction (XRD) confirms that nanopowders of CGO1 and CGO2 are high purity single phase without any trace of un-reacted impurities. The mean crystallite size calculated using XRD Rietveld refinement agrees well with that estimated from the morphologies observed by Transmission Electron Microscopy (TEM). The nominal compositions of CGO1 and CGO2 have been found to be in excellent agreement with that determined by energy dispersive X-ray spectroscopy (EDS) and inductively coupled plasma-atomic emission spectrometry analysis (ICP-AES). The activation energies (E-a = 1.33 and 1.27 eV) and conductivities at 600 and 700 degrees C for CGO1 and CGO2 are also measured. (C) 2012 Elsevier B.V. All rights reserved.