Single-phase GdCo1-xCuxO3-delta (x = 0, 0.15, 0.30) perovskites were prepared by ultrasonic-assisted spray pyrolysis, at a reactor temperature of 950 T. The starting aqueous solutions containing stoichiometric amounts of gadolinium, cobalt and copper nitrates, were atomized using an ultrasonic transducer, operated at a frequency of similar to 1.7 MHz. The aerosol droplets were then transported by O-2 inside a preheated tube furnace, where solvent evaporation and chemical reaction take place. X-ray powder diffraction gave as a result pure GdCo1-xCuxO3-delta (x = 0, 0.15, 0.30) perovskites; this technique also showed that the replacement of Co by Cu increased the unit cell volume. By field emission scanning electron microscopy and transmission electron microscopy, spherical-hollow particles were observed; a detailed inspection showed that the shells are formed by nanoparticles with an average particle size of 49 nm. The substitution of Co by Cu in members with x = 0.15 and 0.30, was confirmed by energy-dispersive X-ray microanalysis. (C) 2005 Elsevier Ltd. All rights reserved.