Formation rate of tetragonal BaTiO3 powder by hydrothermal synthesis and its dielectric property were studied. Submicron tetragonal BaTiO3 powders were prepared hydrothermally, using Ba(OH)(2).8H(2)O, TiO2 (anatase) and KOH as starting chemicals. Characterization via X-ray diffractometry, Field Emission Scanning Electron Microscopy confirmed that increasing calcination temperature (from 1100 to 1300degreesC) promotes the formation of tetragonal BaTiO3. Tetragonal BaTiO3 ceramics obtained from optimum condition (Tetragonal BaTiO3 powders calcined at 1200degreesC for 3 h after hydrothermal synthesized at 200degreesC for 168 h) exhibited submicron size of 0.5-0.7 mum, monodispersed type and high relative permittivity. (C) 2004 Kluwer Academic Publishers.