A crack-free (InNb)(0.1)Ti0.9O2 single crystal of 4 mm in diameter and 30 mm in length was successfully grown by the optical floating zone method. The polycrystalline feed and seed rods for growing the (InNb)(0.1)Ti0.9O2 single crystal were prepared by solid-state reaction method. The oxygen partial pressure significantly affected the crystal quality of the material. As shown in reflecting polarizing microphotographs, crystals grown in air have fewer grain boundaries than those grown in pure oxygen; some air-grown crystals are completely free of grain boundaries. Compared to pure TiO2 crystal, the (Nb+In) co-doped TiO2 crystal required a lower growth rate of 5 mm/h to ensure high quality. (C) 2016 Elsevier B.V. All rights reserved.