The effects of the diameter of a rutile (TiO2) crystal on interface shape during TiO2 crystal growth by the floating zone (FZ) method using a tilting-mirror-type image furnace and on the etch pit density (EPD) of rutile single crystals were examined. To investigate the diameter effect on the interface shape, the grown crystal diameter was varied from 6 to 11 mm at two different tilting angles (theta) of 0 degrees and 20 degrees, respectively. The interface shape was characterized by the convexity (h/r) of interface, where h and r represent the height of the interface and the radius of the grown crystals. The h/r of the crystal-melt interface decreased from 0.15 to 0.0 with an increase in the crystal diameter from 6.5 to 11.2 mm at theta=20 degrees, whereas it increased from 0.45 to 0.58 with an increase in the crystal diameter from 6.0 to 11.0 mm at theta=0 degrees. This result suggests that the molten zone becomes stable at theta=20 degrees for the growth of crystals with a larger diameter. To investigate the crystal diameter effect on the EPD, rutile single crystals with diameters of 10, 16 and 19 mm were grown at theta=20 degrees. The EPDs at the center were 1.0-1.4 x 10(4) cm(-2), which were much smaller than those at the periphery, i.e., 8.0-13.0 x 10(4) cm(-2), for all the grown crystals with different diameters. (C) 2011 Elsevier B.V. All rights reserved.