Three-dimensional (3D) yttrium iodate (YIO3) hollow microspheres consisting of nanotube arrays are synthesized via a one-step hydrothermal process without any surfactants. In the hollow microspheres approximately 5 mu m thick and 15-45 mu m in diameter, the nanotubes in the arrays radiate outward from the center to the edges and are approximately 5 mu m long and 100-200 nm in diameter. The formation of the 3D hollow microspheres can be easily controlled by changing the experimental conditions. The growth mechanisms of the 3D hollow microspheres are discussed in detail, and their optical properties are investigated. (C) 2012 Elsevier B.V. All rights reserved.