The production of zinc by thermal dissociation of zinc oxide has been experimentally investigated in the range of 1700-1950 K using a 10 kW solar chemical reactor directly exposed to concentrated solar radiation. The gaseous products Zn(g) and O-2 exiting the reactor underwent rapid cooling by flowing through an annular water-cooled quench unit and by injection of Ar. XRD analysis along with SEM and TEM images of the solid products deposited at the quenching zone revealed the formation of spherical particles of sizes in the 0.1-30 mu m range, with their surface covered with smaller edged structures, which are characteristic of Zn(g) undergoing condensation followed by Zn(l)/Zn(s) oxidation and coalescence. (C) 2007 Elsevier Ltd. All rights reserved.