Nano-sized BaTiO3 powders with particular Nb concentrations were prepared by hydro-thermal synthesis methods. The structural and dielectric features of the powders were investigated in terms of the dopant content and these were related with each other. The tetragonal fraction of the powders with the Nb-concentration of 0.2 mol% was found to be approximately 45% of that of the pure tetragonal-phased BaTiO3. Lattice spacings were estimated by high-resolution transmission electron microscopy (HRTEM); it was found that there is a significant difference in the relative volume fraction of the tetragonal-phased core region between the powders with and without Nb-dopants. (C) 2011 Elsevier B.V. All rights reserved.