Commercial TiO2 nanoparticles (Degussa P25) with a mean diameter of ca. 20 nm and of predominately anatase phase were deliberately added in sol-gel-prepared amorphous TiO2 particles as "seed'' before being subjected altogether to a mild solvothermal treatment over a temperature range from 100 to 200 degrees C. The presence of seed particles reduced the crystallization temperature moderately from 127.2 to 122.4 degrees C when the seed of up to 10 wt.% was added, resulted in crystalline anatase nanocrystals. On the other hand, crystallite size of the anatase nanocrystals increased up to an average of 28 nm (+40%) with the seed. This seed-induced grain growth appeared to occur preferentially at vicinity of the seed particles. As temperature was raised above the crystallization temperature (similar to 120 degrees C), homogeneous nucleation and growth of the anatase TiO2 nanocrystals prevailed so that a massive anatase structure with a crystal dimension of 8-12 nm resulted after the solvothermal treatment. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.