Synthesis of BaTi4O9 ceramics by a reaction-sintering process was investigated. The mixture of raw materials for stoichiometric BaTi4O9 were pressed and sintered into ceramics without any calcination stage involved. Pure BaTi4O9 phases were obtained at 1150-1280 degrees C. High-sintered density, 98.2-99.5% of theoretical value (4.533 g/cm(3)), can be obtained for pellets sintered at 1200-1280 degrees C for 2-6 h. Some rod-shaped grains 3-7 mu m in the longitudinal axis appear in pellets sintered at 1230 degrees C. Both the size and the amount of these rod-shaped grains increase at higher sintering temperature. (C) 2005 Elsevier Ltd. All rights reserved.