Potassium nickel fluoride (KNiF3) hollow spheres with diameters of 200-400 nm have been solvothermally synthesized at 110degreesC using KF and NiCl2 as reactants in ethanol, without additional template materials or surfactants. The results of XRD and XPS indicate that the products are perovskite-type KNiF3. TEM microphotos show that the hollow spheres are composed of KNiF3 nanoparticles with an average size of 10 nm, and the wall thickness is 20-40 nm. UV-vis and PL spectra have recorded the optical properties of KNiF3 hollow spheres. A possible mechanism for the formation of KNiF3 hollow spheres is also discussed. (C) 2004 Elsevier B.V. All rights reserved.