This paper reports the development of a new process for the synthesis of gadolinium-doped ceria (20GDC) solid solution nanoparticles, as a solid electrolyte for use in solid oxide fuel cells. It is based on high energy milling (mechanical alloying or MA) of CeO(2) and Gd(2)O(3) powders containing 10 mol% Gd(2)O(3). The samples, obtained after different milling times of 10 to 60 h, were characterized by X-ray diffraction (XRD), BET method of the specific surface area measurement, electron microscopy and Raman spectroscopy. The fluorite-structured Ce(0.8)Gd(0.2)O(1.9) solid solution nanopowder with the surface area of 16.86 m(2)/g and particle sizes below 50 nm was obtained by milling the oxide mixture for 30 h. Increase in the milling time beyond 30 h led to the smaller crystallite sizes and more agglomeration. The structural changes, as evidence for the formation of solid solution, which occurred during the course of the milling process, could be appropriately followed and discussed by Raman spectroscopy. (c) 2011 Elsevier B.V. All rights reserved.